Pin heterojunction photovoltaic elements with polycrystal BP(H,F) semiconductor film

ABSTRACT

A pin heterojunction photovoltaic element which generates photoelectromotive force by the junction of a p-type semiconductor layer, an i-type semiconductor layer and an n-type semiconductor layer, characterized that at least one of said p-type and n-type semiconductor layers comprises a polycrystal semiconductor film comprised of boron atoms (B), phosphorus atoms (P), hydrogen atoms (H) optionally fluorine atoms (F), and atoms (M) of a p-type or n-type dopant element, said polycrystal semiconductor film contains crystal grains of an average size in the rage of 50 to 800 Å, and said polycrystal semiconductor film contains the hydrogen atoms (H) in an amount of 0.5 to 7 atomic %; and i-type comprises either (a) a non-single crystal semiconductor film containing silicon atoms (Si) as a matrix and at least one kind of atoms selected from the group consisting of hydrogen atoms (H) and fluorine atoms (F) or (b) a non-single crystal semiconductor film containing silicon atoms (Si) as a matrix, at least one kind of atoms selected from the group consisting of carbon atoms (C) and germanium atoms (Ge), and at least one kind of atoms selected from the group consisting of hydrogen atoms (H) and fluorine atoms (F).

FIELD OF THE INVENTION

The present invention relates to an improved photovoltaic element usableas a power source not only in commercial and home appliances but also inpower supply systems. More particularly, it is concerned with a pinheterojunction photovoltaic element, at least the n-type or p-typesemiconductor layer of which comprises an n-type or p-type polycrystalBP:H(F) semiconductor film which exhibits a high photoelectricconversion efficiency.

BACKGROUND OF THE INVENTION

There have been proposed a variety of photovoltaic elements such assolar cells and power sources for commercial and home appliances. Theyutilize pn junctions formed by ion implantation or thermal diffusion ofimpurities into a single crystal substrate of silicon (Si) or galliumarsenide (GaAs), or by epitaxial growth of an impurity-doped layer onsuch single crystal substrate. However, there is a disadvantage for anyof these photo voltaic elements that they are still costly because ofusing an expensive specific single crystal substrate. Hence, they havenot yet come into general use as solar cells or power sources incommercial and home appliances used by the general public. In order tosolve this problem, there have been proposed a photovoltaic element inwhich there is utilized a pin junction formed by amorphous silicon(hereinafter referred to as "a-Si") semiconductor films laminated on aninexpensive substrate of a non-single crystal material such as glass,metal, ceramic, synthetic resin, etc. by way of a glow dischargedecomposition method. This photovoltaic element does not provide aphotoelectric conversion efficiency as high as that provided by theforegoing pn junction photovoltaic element in which a single crystalsubstrate is used. However, this photovoltaic element can be relativelyeasily produced and is of low production cost, and because of this, itis used as a power source in some kinds of appliances with very smallpower consumption such as electronic calculators and wrist watches.

In this pin junction amorphous silicon photovoltaic element, the Fermilevel of the a-Si semiconductor having a good photoconductive propertylies a little toward the conduction band from the center of the band gapand the electric field strength at the interface of the p-i junction isgreater than that at the interface of the n-i junction. In this respect,it is advantageous to impinge light from the side of the p-typesemiconductor layer in order to provide a desirable photoelectricconversion efficiency.

For the p-type semiconductor layer, it is desired to be formed of such asemiconductor film that does not absorb light and does not have defectssince the light to be absorbed within the p-type semiconductor layerdoes not contribute to generation of photoelectric current in the casewhere defects acting as recombination centers are present therein. Inview of this, for the semiconductor film to constitute the p-typesemiconductor layer in the pin junction a-Si photovoltaic element,studies have been made on amorphous silicon carbide films (hereafterreferred to as "a-SiC film") which are of wide band gap and also onmicrocrystal line silicon films (hereinafter referred to as "μC-Sifilm") which are known as indirect semiconductor films having smallabsorption coefficients and which are considered to hardly absorb lightwhen they are of 100 to 200 Å in thickness even in the case where theyare of narrow band gap. As for the a-SiC semiconductor film, there is anadvantage that its band gap can be widened by increasing the compositionratio of the constituent carbon atoms. However, there is a disadvantagethat when its band gap is more than 2.1 eV, its film quality is markedlyworsened. Therefore, there is a limit for the a-SiC semiconductor filmto be used as the p-type semiconductor layer in a pin heterojunctionphotovoltaic element.

As for the uC-Si semiconductor film, there is still a disadvantage thatits band gap is narrow in any case and the quantity of light absorbedthereby is remarkable. Particularly, when the incident light is suchthat it contains short-wavelength light in a large proportion, thequantity of light absorbed becomes great.

In view of this, in order to provide a desirable pin heterojunctionphotovoltaic element of the type wherein light is impinged from the sideof the p-type semiconductor layer, it necessitates the use of a p-typesemiconductor film having a desirably wide band gap and a minimizeddefect density as the p-type semiconductor layer.

The same situation is present also in the case of a pin heterojunctionphotovoltaic element of the type wherein light is impinged from the sideof the n-type semiconductor layer. That is, the n-type semiconductorlayer is required to be constituted by such an n-type semiconductor filmhaving a desirably wide band gap and a minimized defect density.

Further, in the case of a so-called tandem stacked type photovoltaicelement or a triple cell tandem stacked type photovoltaic elementcomprising a plurality of stacked cells being stacked, each cell ofwhich comprises a pin heterojunction photovoltaic element in which theresidual components of light which are left not absorbed by the uppercell are absorbed by the lower cell to obtain a sufficient photoelectricconversion, both the p-type semiconductor layer and the n-typesemiconductor layer of each of the cells are required to have adesirably wide band gap and a minimized defect density.

Further, for any of the foregoing photovoltaic elements, it is requiredfor the material to constitute the p-type or n-type semiconductor layerto be such that it can be directly deposited on a non-single crystalsubstrate of glass, metal, ceramic or synthetic resin in a desired stateand does not give any negative effect to the i-type semiconductor layerlaminated thereon.

As semiconductor films capable of providing a wide band which satisfythe foregoing requirements, BP semiconductor films have been proposed byJapanese Patent Laid-open No. 116673/1981 (called "literature 1"hereinafter), Japanese Patent Laid-open No. 189629/1986 (called"literature 2" hereinafter) and Japanese Patent Laid-open No.189630/1986 (called "literature 3" hereinafter).

That is, literature 1 mentions a pin heterojunction solar cell in whicheither the p-type or n-type semiconductor layer is comprised of a p-typeor n-type amorphous BP semiconductor film (that is, a-BP semiconductorfilm) prepared by the glow discharge decomposition method and the i-typesemiconductor layer is comprised of a a-Si semiconductor film containingfluorine atoms (F). Literature 1 does not mention anything about acrystalline BP semiconductor film (that is, poly-BP semiconductor film)which is to be distinguished from said a-BP semiconductor film. Inaddition, literature 1 does not describe anything about thecharacteristics required for a solar cell for the said pinheterojunction photovoltaic element. Literatures 2 and 3 are concernedwith methods of forming semiconductor films containing group III-Velements of the Periodic Table by way of the HR-CVD method (HydrogenRadical Assisted CVD method). But none of literatures 3 and 4 mentionsanything about BP semiconductor films.

Further, none of literatures 1 to 3 mentions a tandem type photovoltaicelement or a triple cell tandem stacked type photovoltaic element.

Against this background, there is an increased social demand to providean inexpensive photovoltaic element which exhibits a high photoelectricconversion efficiency particularly for short wavelength light and whichis practically usable as a solar cell and also as a power source invarious appliances.

SUMMARY OF THE INVENTION

The present invention is aimed at solving the foregoing problemsrelating to photovoltaic elements for use in solar cells and otherappliances and satisfying the foregoing social demand.

It is therefore an object of the present invention to provide animproved pin heterojunction photovoltaic element usable in devicestypified by a solar cell using an improved BP semiconductor film whichmay be desirably formed even on a commercially available inexpensivenonsingle crystal substrate of glass, metal, ceramics or synthetic resinand which may form a desired pin junction with other films formed onsuch substrate.

Another object of the present invention is to provide an improved pinheterojunction photovoltaic element based on the improved BPsemiconductor film which provides a high photoelectric conversionefficiency particularly for short-wavelength light and which is usablein devices typified by a solar cell.

BRIEF DESCRIPTION OF THE DRAWINGS 7 FIG. 1(A) is a schematicrepresentation showing a typical layer structure of a pin heterojunctionphotovoltaic element according to the present invention.

FIG. 1(B) is a schematic representation showing another typical layerstructure of a pin heterojunction photovoltaic element according to thepresent invention.

FIG. 1(C) is a schematic representation showing a typical multi-celltandem stacked structure of a pin heterojunction photovoltaic elementaccording to the present invention.

FIG. 2 is a schematic diagram showing the apparatus for forming adeposited film by way of a HR-CVD method of the present invention.

FIG. 3 is a schematic diagram showing the apparatus for forming adeposited film by way of a reactive sputtering method of the presentinvention.

FIG. 4 is a schematic diagram showing the apparatus for forming adeposited film by way of a plasma CVD method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have made extensive studies for overcoming theforegoing problems of the known BP semiconductor films for use invarious devices such as solar cells and attaining the objects asdescribed above and as a result, have accomplished the present inventionbased on the findings obtained through various experiments as belowdescribed.

That is, as a result of preparing a polycrystal BP semiconductor film inwhich a specific amount of hydrogen atoms was incorporated, optionally aspecific amount of fluorine atoms was additionally incorporated, and theaverage size of crystal grains is controlled to a specific value (thisdeposited film is hereinafter referred to as "poly-BP:H(F) film"), thepresent inventors have found that (a) the poly-BP:H(F) film may beformed in a desired state even on a non-single crystal substrate ofglass, metal, ceramics or synthetic resin: (b) the poly-BP:H(F) filmformed on such non-single crystal substrate is accompanied with very fewdefects: (c) it can be easily and efficiently doped with a dopant ofp-type or n-type: and (d) when doped with such dopant, there is affordeda desirable high quality p-type or n-type poly-BP:H(F) semiconductorfilm many practically applicable semiconductor characteristics.

The present inventors have further found that in the case of using theforegoing poly-BP:H(F) film as a member of a pin heterojunctionphotovoltaic element, there is afforded a pin heterojunctionphotovoltaic element which efficiently and stably generates a desiredphotoelectromotive force.

The present invention has been completed on the basis of these findings,and it provides pin heterojunction photovoltaic elements as are belowmentioned. (1) A pin heterojunction photovoltaic element which generatesphotoelectromotive force by the junction of a p-type semiconductorlayer, an i-type semiconductor layer and an n-type semiconductor layer,characterized in that at least one of said p-type and n-typesemiconductor layers comprises a polycrystal semiconductor filmcomprised of boron atoms (B), phosphorus atoms (P), hydrogen atoms (H),optionally fluorine atoms (F), and atoms (M) of a p-type or n-typedopant element: said semiconductor film contains crystal grains of anaverage size in the range of 50 to 800 Å: and said semiconductor filmcontains the hydrogen atoms (H) in an amount of 0.5 to 7 atomic % (thispolycrystal semiconductor film will be hereinafter referred to as"poly-BP: H(F):M film"): and said i-type layer comprises a non-singlecrystal semiconductor film containing silicon atoms (Si) as a matrix andat least one kind of atoms selected from the group consisting ofhydrogen atoms (H) and fluorine atoms (F). Said non-single crystalsemiconductor film includes amorphous semiconductor films, microcrystalsemiconductor films, and polycrystal semiconductor films, and it will behereinafter referred to as "Non-Si(H,F) film". (2) A pin heterojunctionphotovoltaic element which generates photoelectromotive force by thejunction of a p-type semiconductor layer, an i-type semiconductor layerand an n-type semiconductor layer, characterized in that at least one ofsaid p-type and n-type semiconductor layers comprises the foregoingpoly-BP:H(F):M semiconductor film: and said i-type semiconductor layercomprises a non-single crystal semiconductor film containing siliconatoms (Si) as a matrix, at least one kind of atoms selected from thegroup consisting of carbon atoms (C) and germanium atoms (Ge), and atleast one kind of atoms selected from the group consisting of hydrogenatoms (H) and fluorine atoms (F) (this film will be hereinafter referredto as "Non-Si(C,Ge)(H,F) semiconductor film"). This Non-Si(C,Ge)(H,F)semiconductor film includes a-Si(C,Ge)(H,F) semiconductor films,uC-Si(C,Ge)(H,F) semiconductor films, and poly-Si(C,Ge)(H,F)semiconductor films.

Any of the foregoing pin heterojunction photovoltaic elements (1) and(2) according to the present invention stably provides a highphotoelectric conversion efficiency particularly for short-wavelengthlight and enables the obtainment of a large Isc at a high Voc. Inaddition, any of the foregoing pin heterojunction photovoltaic elements(1) and (2) according to the present invention may be a multi-celltandem stacked photovoltaic element, each cell comprising the foregoingpin heterojunction photovoltaic element (1) or (2). The pinheterojunction photovoltaic element according to the present inventionalways exhibits its functions even upon repeated use for a long periodof time without deterioration and thus, it can be practically used as apower source to supply electric power.

The experiments carried out by the present inventors will be detailed inthe following.

EXPERIMENT A

Studies on the method of forming a poly-BP:H(F) film.

The present inventors have prepared poly-BP:H(F) films by each of thefollowing three processes (1) to (3).

Process (1) by HR-CVD method

This process (1) forms a poly-BP:H(F) film by using a B-containingprecursor from a B-containing raw material gas, a P-containing precursorfrom a P-containing raw material gas, hydrogen radicals from hydrogengas (H₂), optionally fluorine radicals from a F-containing raw materialgas and chemically reacting them in a film-forming space containing asubstrate on which a film is to be deposited to form a poly-BP:H(F) filmon the substrate maintained at a desired temperature.

This process (1) is practiced by using an appropriate HR-CVD apparatushaving a structure as shown in FIG. 2.

The HR-CVD apparatus shown in FIG. 2 comprises a film-forming chamber201 in which is installed a substrate holder 202. There is shown asubstrate 203 which is fixed onto the substrate holder 202. Thesubstrate 203 is heated by radiation from an infrared heater 205, whilebeing monitored by a thermo-couple 204.

The substrate holder 202 is transferred to the other film-formingchamber 222 or a load lock chamber 212 through a gate valve 207 by asubstrate transfer unit 206. Reference numeral 208 stands for a firstactivation chamber connected through a transport conduit 217 to thefilm-forming chamber 201.

To the activation chamber 208, a gas supply pipe 214 extending from agas reservoir containing, for example, a B-containing raw material gas(not shown) is connected. The first activation chamber 208 is providedwith an activation energy generation means 211 to apply an activationenergy such as an electric energy of direct current, high-frequency ormicrowave, heat energy or light energy to said B-containing raw materialgas supplied into the first activation chamber 208, to thereby produceB-containing precursors, which are successively transported through thetransport conduit 217 into the film-forming chamber 201.

Likewise, reference numeral 209 stands for a second activation chamberconnected through a transport conduit 218 to the film-forming chamber201. To the second activation chamber 209, a gas supply pipe 215extending from a gas reservoir containing, for example, H₂ gas (notshown) is connected.

The second activation chamber 209 is provided with an activation energygeneration means 212 to apply an activation energy such as an electricenergy of direct current, high-frequency or microwave, heat energy orlight energy to said H₂ gas supplied into the second activation chamber209, to thereby produce hydrogen radicals, which are successivelytransported through the transport conduit 218 into the film-formingchamber 201.

Further, reference numeral 210 stands for a third activation chamberconnected through a transport conduit 219 to the film-forming chamber201. Reference numeral 216 stands for a gas supply pipe extending from agas reservoir containing, for example, a P-containing raw material gas(not shown) which is connected to the third activation chamber 210. Thethird activation chamber 210 is provided with an activation energygeneration means 213 to apply an activation energy such as an electricenergy of direct current, high-frequency or microwave, heat energy orlight energy to said P-containing raw material gas supplied into thethird activation chamber 210, to thereby produce P-containingprecursors, which are successively transported through the transportconduit 219 into the film-forming chamber 201.

The foregoing B-containing precursors, P-containing precursors andhydrogen radicals thus introduced into the film-forming chamber 201 aremixed and chemically reacted to form a semiconductor film on thesubstrate 203 maintained at a desired temperature. The film-formingchamber 201 is provided with an exhaust pipe connected through anexhaust valve 220 to a vacuum pump 221. Reference numeral 223 stands fora pressure gage provided with the film-forming chamber 201, which servesto monitor the inner pressure of the film-forming chamber 201.

Now, by the HR-CVD method practiced in the foregoing HR-CVD apparatusshown in FIG. 2, there were prepared ten kinds of semiconductor filmscontaining B and P (Samples Nos. 1 to 10) under the conditions shown inTable 1. In each case, there was used a Corning No. 7059 glass plate of2 (inch) by 2 (inch) in size and 0.8 mm in thickness (product by CorningGlass Works Co.) as the substrate 203. The raw material gas (A) shown inTable 1 i.e. B(CH₃)₂ gas and He gas (as a dilution gas) were suppliedthrough the gas supply pipe 214 into the first activation chamber 208.PF₅ gas (raw material gas B in Table 1) was supplied through the gassupply pipe 216 into the third activation chamber 210. And H₂ gas and Hegas (raw material gas (C) in Table 1) were supplied through the gassupply pipe 215 into the second activation chamber 209.

For each of the resultant semiconductor film samples Nos. 1 to 10, thefilm sample was cut into six equal parts.

The first cut part was subject to measurement of the hydrogen content inthe film by a SIMS apparatus (trade name: IMS-3f, product by CAMEA Co.,Ltd.). The second cut part was set to a X-ray microanalyzer EPM-810Q(product by Shimazu Seisakusho K.K.) to determine the distributed statesand the composition ratio of B to P in the film. The third cut part wassupplied to an X-ray diffractometer RAD IIB (product by Rigaku DenkiK.K.) to determine the crystal orientation and the size of the crystalgrains in the film.

The results obtained are collectively shown in Table 2.

From the results shown in Table 2, there have been obtained thefollowing findings. That is, it has been firstly recognized that thehydrogen content, the fluorine content and the sizes of crystal grainsin the film can be properly controlled by regulating the flow rate of H₂gas to be introduced into the second activation chamber 209.

Then, in the case of each of the film samples Nos. 1 and 2 which wereprepared with the respective flow rates of 0 sccm and 0.2 sccm for theH₂ gas, it has been found that since supply of the hydrogen radicalsinto the reaction system is zero or small, the hydrogen content in thefilm is zero or small but the fluorine content therein is relativelylarge, B and P are distributed in localized states and the filmstructure is random and does not have a crystal orientation.

As for the film samples Nos. 3 to 7, it has been found that thecomposition ratio of the B to the P in the film satisfies thestoichiometric ratio with the flow rate of H₂ gas being increasedwherein a crystal orientation is caused and the sizes of crystal grainsare enlarged accordingly.

As for the film samples Nos. 8 to 10 which were prepared with anincreased flow rate of the H₂ gas, a tendency has been found that supplyof hydrogen radicals into the reaction system becomes excessive andcauses negative influences for the film to be deposited such as etchingand because of this, the size of the crystal grains is reduced and thehydrogen content also is reduced.

In consequence, it has been recognized that the amount of hydrogenradical to be supplied into the reaction system plays an important rolein forming the film.

In addition to the above, other facts have also found through furtherexperiments by the present inventors. That is, changes in thefilm-forming parameters i.e. the substrate temperature, the innerpressure, the activation energy power (microwave power) to be applied,the flow rate of a dilution gas (He gas), the distance between thesubstrate and the outlet of the transport conduit, the kinds of the rawmaterial gases to be used also contribute somewhat to control of thehydrogen content, the fluorine content and the sizes of crystal grainsin the film.

Process (2) by reactive sputtering method

This process (2) forms a poly-BP:H(F) film by introducing Ar gas and H₂gas, and optionally F₂ gas or HF gas in combination into a film-formingchamber in which a substrate is placed and a cathode electrode having atarget comprising a single crystal or polycrystal BP wafer plate orother single crystal or polycrystal wafer plate dosed with hydrogenatoms (H) or and fluorine atoms (F) by ion implantation thereon isplaced at a position opposite to the substrate, applying a highfrequency voltage to the cathode to form a plasma atmosphere in thespace between the substrate and the BP wafer plate, sputtering the BPwafer plate with the plasma to release boron atoms (B) and phosphorusatoms (P) and chemically reacting the boron atoms (B), phosphorus atoms(P), hydrogen atoms (H) and optional fluorine atoms (F) present in theplasma to cause the formation of said film on the substrate maintainedat a desired temperature.

Process (2) is practiced by using an appropriate reactive sputteringapparatus having such a structure as shown in FIG. 3.

The reactive sputtering apparatus shown in FIG. 3 comprises afilm-forming chamber 301 in which is installed a substrate holder 302.There is shown a substrate 303 which is fixed onto the substrate holder302. The substrate 303 is heated by radiation from an infrared heater305, while being monitored by a thermo-couple 304. The substrate holder302 is transferred to the other film-forming chamber 317 or a load lockchamber 313 through a gate valve 307 by a substrate transfer unit 306.The substrate 303 is electrically grounded through the substrate holder302 as shown in FIG. 3. Reference numeral 312 stands for a cathodeelectrode having a target 316 comprising, for example, a single crystalor polycrystal BP wafer plate, placed thereon. The cathode electrode 312is connected through a matching box 311 to a high frequency power source310. The film-forming chamber 301 is provided with a gas supply pipe 308for introducing sputtering gases such as Ar gas, H₂ gas, F₂ gas, etc.into the film-forming chamber. The film-forming chamber 301 is furtherprovided with an exhaust pipe connected through a exhaust valve 314 to avacuum pump 315. Reference numeral 309 stands for a pressure gageprovided with the film-forming chamber 301, which serves to monitor theinner pressure of the film-forming chamber 301.

Now, by the reactive sputtering method practiced in the foregoingsputtering apparatus shown in FIG. 3, there were prepared ten kinds ofsemiconductor films containing B and P (Samples Nos. 11 to 20) under theconditions shown in Table 3.

In each case, there was used a Corning No. 7059 glass plate of 2 (inch)by 2 (inch) in size and 0.8 mm in thickness as the substrate 303.

For each of the resultant film samples Nos. 11 to 20, the film samplewas cut into six equal parts, three of them were subjected to theevaluations in the same manners as in the above case.

The results obtained are collectively shown in Table 4.

From the results shown in Table 4, there have been obtained thefollowing findings. That is, it has been firstly recognized that thehydrogen content, the fluorine content and the sizes of crystal grainsin the film can be properly controlled by regulating the flow rate of H₂gas or/and HF gas introduced into the film-forming chamber 301.

Then, for the case of the film sample No. 11 which was prepared withintroduction of neither H₂ gas nor HF gas, it has been recognized thatneither hydrogen radicals nor fluorine radicals are present in theplasma atmosphere formed in the film-forming chamber 301 and because ofthis, the resultant film contains neither hydrogen atoms nor fluorineatoms, the composition ratio of B to P does not satisfy thestoichiometric ratio and the B and the P are distributed in localizedstates in the film, and the film structure is random and does not have acrystal orientation.

Likewise, in the case of the film sample No. 12 which was prepared withintroduction of H₂ gas and HF gas respectively at a flow rate of 1 sccm,it has been recognized that both hydrogen radicals and fluorine radicalsare not present in a sufficient amount in the plasma atmosphere formedin the film-forming chamber 301 and because of this, although theresultant film contains a certain amount of hydrogen atoms, thecomposition ratio of the B to the P does not satisfy the stoichiometricratio and the average size of crystal grains in the film is undesirablysmall.

On the other hand, for the film samples Nos. 13 to 18, it has beenrecognized that the more at least the flow rate of H₂ gas increases, themore the composition ratio of the B to the P satisfies thestoichiometric ratio and the distributed states of the B and the P areimproved, and in addition, the average size of crystal grains isdesirably enlarged and the film contains desired amounts of hydrogenatoms and optional fluorine atoms.

However, for the film samples Nos. 19 and 20 which were prepared withexcessive flow rates of H₂ gas and HF gas, a tendency has beenrecognized that excessive amounts of hydrogen radicals and fluorineradicals are present in the plasma atmosphere formed in the film-formingchamber 301 and because of this, the average size of crystal grains isundesirably reduced, and both the hydrogen content and the fluorinecontent are undesirably increased.

In consequence, it has been recognized that the amount of hydrogenradicals present in the plasma atmosphere formed in the reaction systemplays an important role and the chemical reactions causing the formationof the film are enhanced when fluorine radicals are present togetherwith hydrogen radicals in the above plasma atmosphere formed in thereaction system, thereby resulting in forming desired poly-BP:H(F)films.

In addition to the above, other facts have been also found throughfurther experiments by the present inventors. That is, changes in thefilm-forming parameters i.e. the substrate temperature, the innerpressure, the high frequency power to be applied, the flow rates ofsputtering gases to be used, the distance between the target and thesubstrate and the like also contribute somewhat to control of thehydrogen content, the fluorine content and the average size of crystalgrains in the film.

Process (3) by plasma CVD method

This process (3) forms a poly-BP:H(F) film by introducing a B-containingraw material gas (A), a P-containing raw material gas (B) and H₂ gas(C), and optionally a further gas such as HF gas or F₂ gas into afilm-forming chamber in which a substrate on which a film is to beformed is placed and a cathode electrode is installed, applying a highfrequency voltage to the cathode to cause glow discharge plasmas bywhich the raw material gases are decomposed to cause the formation ofsaid film on the substrate maintained at a desired temperature.

This process (3) is practiced by using an appropriate plasma CVDapparatus having a structure as shown in FIG. 4.

The plasma CVD apparatus shown in FIG. 4 comprises a film-formingchamber 401 in which is installed a substrate holder 402. There is showna substrate 403 which is fixed onto the substrate holder 402. Thesubstrate 403 is heated by radiation from an infrared heater 405, whilebeing monitored by a thermo-couple 404. The substrate holder 402 istransferred to the other film-forming chamber 416 or a load lock chamber413 through a gate valve 407 by a substrate transfer unit 406. Referencenumeral 412 stands for a cathode electrode which is placed at theposition opposite to the substrate 403. The cathode electrode 412 isconnected through a matching box 411 to a high frequency power source410. The film-forming chamber 401 is provided with a gas supply pipewhich is connected through a plurality of feed pipes 408, 409 to aplurality of gas reservoirs (not shown). The film-forming chamber 401 isfurther provided with an exhaust pipe connected through an exhaust valve414 to a vacuum pump 415. Reference numeral 417 stands for a pressuregage provided with the film-forming chamber 401, which serves to monitorthe inner pressure of the film-forming chamber 401.

Now, by the plasma CVD method practiced in the foregoing plasma CVDapparatus shown in FIG. 4, there were prepared ten kinds of BP systemsemiconductor films (Samples Nos. 21 to 30) under the conditions shownin Table 5. In each case, there was used a Corning No. 7059 glass plateof 2 (inch) by 2 (inch) in size and 0.8 mm in thickness as the substrate403.

B(CH₃)₃ gas and He gas (as a dulation gas) (raw material gas (A) inTable 5) were supplied into the film-forming chamber 401 through thefeed pipe 408. Other raw material gases, i.e. PH₃ gas (raw material gas(B) in Table 5), and H₂ gas and HF gas (raw material gas (C) in Table 5)were supplied into the film-forming chamber 401 through the feed pipe409.

For each of the resultant film samples Nos. 21 to 30, the film samplewas cut into six equal parts, the three parts of which were subjected tothe evaluations in the same manners as in the foregoing case of theprocess (1).

The results obtained are collectively shown in Table 6.

From the results shown in Table 6, there have been obtained thefollowing findings.

That is, it has been firstly recognized that the hydrogen content, thefluorine content and the average size of crystal grains in the film canbe properly controlled by regulating the flow rate of the raw materialgas (C) i.e. principally H₂ gas and also HF gas introduced into thefilm-forming chamber 401.

Then, for the case of the film sample No. 21 which was prepared withintroduction of neither the H₂ gas nor HF gas, it has been recognizedthat because neither the H₂ gas nor the HF gas is used, the resultantfilm is amorphous, the B and the P are distributed in localized statesand the film contains an undesirably large amount of hydrogen atoms dueto the influence caused by the residual --CH₃ group in the reactionsystem.

Likewise, for the case of the film sample No. 22 which was prepared withintroduction of H₂ gas at a flow rate of 5 sccm, it has been recognizedthat because the amount of hydrogen radicals present in the plasmaatmosphere formed in the reaction system is insufficient, the resultantfilm is amorphous, the B and P are distributed in localized states andthe film contains an undesirably large amount of hydrogen atoms mainlydue to the influence caused by the residual --CH₃ group in the reactionsystem. Further, for the case of the film sample No. 23 which wasprepared by introducing H₂ gas and HF gas into the film-forming chamber401 respective at a flow rate of 10 sccm, it has been recognized thatbecause the amount of hydrogen radical present in the plasma atmosphereformed in the reaction system is still insufficient, the resultant filmis still amorphous and although the hydrogen content in the film isdesirable, the B and the P are not desirably distributed but uneven.

On the other hand, for the film samples Nos. 24 to 28 which wereprepared by introducing H₂ gas at respective flow rates of 100, 100,200, 300 and 500 and HF gas at respective flow rates of 50, 80, 100, 30and 30 into the film-forming chamber 401, each of the films containsdesirable amounts of hydrogen atoms and fluorine atoms, the compositionratio of the B to the P satisfies the stoichiometric ratio, the B andthe P are evenly distributed in the film, the film has a desirableorientation and contains a desirable average size of crystal grains.However, for the film samples Nos. 29 and 30 which were prepared withexcessive flow rates of H₂ gas, a tendency has been recognized thatthere is present an excessive amount of hydrogen radicals in the plasmaatmosphere formed in the reaction system and because of this, reductionin the average size of crystal grains in the film is caused.

In consequence, it has been recognized that the amount of hydrogenradicals present in the plasma atmosphere upon forming the poly-BP: H(F)films plays an important role and the chemical reactions to cause theformation of said film are enhanced when fluorine radicals are presenttogether with hydrogen radicals in the plasma atmosphere formed in thereaction system, thereby resulting in forming a desired poly-BP: H(F)film.

In addition to the above, other facts have been also found throughfurther experiments by the present inventors. That is, changes in thefilm-forming parameters i.e. the substrate temperature, the innerpressure, the high frequency power to be applied, the flow rates and thekinds of the raw material gases (A),(B) and (C), the distance betweenthe substrate and cathode, and the like also contribute somewhat tocontrol the hydrogen content, the fluorine content and the average sizeof crystal grains in the film.

EXPERIMENT B Observations of the Interrelations Among VariousCharacteristics, The Content of Hydrogen Atoms, The Content of OptionalFluorine Atoms, and The Average Size of Crystal Grains For The DepositedFilm

Each of the foregoing film samples Nos. 1 to 30 was examined fordeterioration in its characteristics under light irradiation.

The examination was carried out using one of the remaining cut threeparts.

Prior to the examination, a comb-shaped Cr electrode was formed on eachspecimen by vacuum deposition. The resultant was exposed to AM-1 light(100 mW/cm²) for 8 hours to examine the ratio of change Δσ in theelectric conductivity (σ) after irradiation with the AM-1 light for 8hours versus the initial value (σ_(i)), that is Δσ=σ_(e) /σ_(i), whereσ_(e) is the value after irradiation with the AM-1 light for 8 hours.

The results for the ratio of change Δσ are collectively shown in Table7. For this evaluation item in Table 7, the symbol "O" means the casewhere Δσ≧0.95, the symbol "Δ" means the case where 0.9≦Δσ<0.95 and thesymbol "X" means the case where Δσ<0.9.

Then, each of the foregoing film samples Nos. 1 to 30 was examined forthe content of an impurity in the following way. That is, in each case,one of the remaining two cut parts was placed in a cryostat andirradiated with light from a UV lamp (1 KW) at a temperature of 7.7 K toexamine photoluminescence.

This evaluation was made based on the ratio ΔI between the intensityI_(R) of a spectrum from the film sample No. 11 as the control and theintensity Is of a spectrum from the other film sample (that is,ΔI=Is/I_(R)) and the number of the spectra. The results for thephotoluminescence are collectively shown in Table 7. For this evaluationitem in Table 7, the symbol "O" means the case where ΔI≦0.3, the symbol"Δ" means the case where 0.3<ΔI≦0.7, and the symbol "X" means the casewhere ΔI>0.7.

Finally, each of the foregoing film samples Nos. 1 to 30 was examinedfor surface smoothness in the following way. That is, in each case, theremaining last cut part was placed in a FE-SEM (trade name:field-emission scanning electron microscope S-900, produced by HitachiSeisakusho K.K.) to examine the minute structure of the surface of thefilm. The results are collectively shown in Table 7.

For this evaluation item in Table 7, the symbol "O" means the case wherecrystal grains are uniformly distributed, and surface roughness and pinholes are not present, and the symbol "X" means the case where anycrystal grains are not observed, crystal grains are unevenlydistributed, and/or roughness and pin holes are observed.

In addition, the above results were combined to totally evaluate each ofthe film samples Nos. 1 to 30. The totally evaluated results arecollectively shown in the column "total evaluation" of Table 7. For thisevaluation in Table 7, the symbol "O" means the case where the totalevaluation was concluded to be excellent, the symbol "○" means the casewhere the total evaluation was concluded to be good, the symbol "Δ"means the case where the total evaluation was concluded to be fairlygood, and the symbol "X" means the case where the total evaluation wasconcluded to be not good.

From the results shown in Table 7, it has been considered that the filmsamples which were evaluated as being excellent or good in the totalevaluation are desirably usable as constituent element members invarious electronic devices including photovoltaic devices. And it hasbeen confirmed that each of these film samples contains hydrogen atomsin an amount of 0.5 to 7 atomic %, optional fluorine atoms in an amountof 0 to 3 atomic %, and crystal grains of an average size in the rangeof 50 to 800 Å.

EXPERIMENT C Observations of the doping properties of the BP:H(F) film

(1) n-type doping properties

The foregoing procedures for preparing the film samples No. 1 to 10 bythe HR-CVD method were repeated, except that liquid Se(CH₃)₂ wasgasified by feeding He gas (as a carrier gas) into said liquid Se(CH₃)₂in a bubbling vessel (not shown) to generate a gas comprising Se(CH₃)₂saturated with He gas (hereinafter referred to as "Se(CH₃)₂ /He gas")and this Se(CH₃)₂ /He gas was additionally used as an n-typedopant-imparting raw material gas together with the raw material gas (A)in Table 1 and said Se(CH₃)₂ /He gas was introduced into the firstactivation chamber 208 at a flow rate of 2.4×10⁻¹⁰ mol/min together withthe raw material gas (A), to thereby obtain ten BP:H(F):Se film samples(Samples Nos. 31 to 40).

Likewise, ten BP:H(F):Se film samples (Samples Nos. 41 to 50) wereprepared by repeating the foregoing procedures for preparing the filmsamples Nos. 11 to 20 by the reactive sputtering method, except forusing said Se(CH₃)₂ /He gas in addition to the sputtering gases shown inTable 3 and introducing said Se(CH₃)₂ /He gas at a flow rate of4.8×10⁻¹¹ mol/min together with the sputtering gases into thefilm-forming chamber 301.

Further, ten BP:H(F): Se film samples (Samples Nos. 51 to 60) wereprepared by repeating the foregoing procedures for preparing the filmsamples 21 to 30 by the plasma CVD method, except for using saidSe(CH₃)₂ /He gas in addition to the raw material gas (A) shown in Table5 and introducing said Se(CH₃)₂ /He gas at a flow rate of 1.2×10⁻¹⁰mol/min together with the raw material gas (A) into the film-formingchamber 401.

Each of the film samples Nos. 31 to 60 thus obtained was examined withrespect to various evaluation items in the same manners as in the aboveExperiments A and B. Each was also examined for conduction type by aconventional thermo-electric power measuring method.

As a result, the film samples Nos. 34 to 38 (which are correspond to theforegoing film samples Nos. 4 to 8), the film samples Nos. 43 to 48(which correspond to the foregoing film samples Nos. 13 to 18), and thefilm samples Nos. 55 to 58 (which correspond to the foregoing filmsamples Nos. 25 to 28) were found to be excellent or good in the totalevaluation. Specifically, each of these film samples was verysatisfactory, with the hydrogen content in the range of 0.5 to 7 atomic%, the fluorine content in the range of 0 to 3 atomic %, the averagesize of crystal grains, the ratio of change in the electric conductivityand the photoluminescence, and it had a desirable crystal orientation.And each of these film samples exhibited a desirable n-typeconductivity.

The average size of crystal grains contained in these film samples wasfound to be in the range of 50 to 800 Å. Separately, as a result ofexamining the quality of each of these film samples doped with an n-typedopant (Se), it has been found that each of the film samples containingfluorine atoms (F) exhibits an improved heat resistance.

(2) p-type doping properties

The foregoing procedures for preparing the film samples Nos. 1 to 10 bythe HR-CVD method were repeated, except that there was used Zn(CH₃)₂(hereinafter referred to as "DMZn") as a p-type dopant-imparting rawmaterial gas. It was gasified by introducing He gas as a carrier gasinto the DMZn contained in a bubbling vessel (not shown) and theresultant gas was introduced at a flow rate of 4.3×10⁻¹⁰ mol/min intothe activation chamber 208 together with the raw material gas (A) inTable 1, to thereby obtain ten BP:H(F):Zn film samples (Samples Nos. 61to 70).

Likewise, ten BP:H(F):Zn film samples (Samples Nos. 71 to 80) wereprepared by repeating the foregoing procedures for preparing the filmsamples Nos. 11 to 20 by the reactive sputtering method, except forusing DMZn, gasifying it with the use of He gas and introducing theresultant gas containing DMZn at a flow rate of 6.8×10⁻¹¹ mol/min intothe film-forming chamber 301 together with the sputtering gases shown inTable 3.

Further, ten BP:H(F):Zn film samples (Sample Nos. 81 to 90) wereprepared by repeating the foregoing procedures for preparing the filmsamples Nos. 21 to 30 by the plasma CVD method, except for using DMZn,gasifying it with the use of He gas and introducing the resultant gascontaining DMZn at a flow rate of 2.4×10⁻¹⁰ mol/min into thefilm-forming chamber 401 together with the raw material gas (A) shown inTable 5.

Each of the film samples Nos. 61 to 90 thus obtained was examined withrespect to various evaluation items in the same manners as in the aboveExperiments A and B. It was also examined for conduction type by aconventional thermo-electric power measuring method.

As a result, the film samples No. 64 to 68 (which corresponding to theforegoing film samples Nos. 4 to 8), the film samples Nos. 73 to 78(which correspond to the foregoing film samples Nos. 13 to 18), and thefilm samples Nos. 85 to 88 (which correspond to the foregoing filmsamples Nos. 25 to 28) were found to be excellent or good in the totalevaluation. Specifically, each of these film samples was verysatisfactory, with the hydrogen content in the range of 0.5 to 7 atomic%, the fluorine content in the range of 0 to 3 atomic %, the averagesize of crystal grains, the ratio of change in the electric conductivityand the photoluminescence, and it had a desirable crystal orientation.Each of these film samples exhibited a desirable p-type conductivity.The average size of crystal grains contained in each of these filmsamples was found to be in the range of 50 to 800 Å. Separately, as aresult of examining the quality of each of these film samples doped witha p-type dopant (Zn), it has been found that each of the film samplescontaining fluorine atoms (F) exhibits an improved heat resistance.

Not only from the above results obtained through the above experimentsbut also from the results obtained through further studies, it has beenrecognized that a desirable poly-BP:H(F):M semiconductor film (where Mis a dopant of n-type or p-type) in which the B and the P are evenlydistributed and the composition ratio of the B to the P satisfies thestoichiometric ratio and which contains crystal grains of a desiredaverage size and has a desired crystal orientation can be effectivelyobtained by the foregoing HR-CVD method, reactive sputtering method orplasma CVD method in which the amount of hydrogen radicals present inthe plasma atmosphere formed in the reaction system is properlycontrolled. And in the case where fluorine radicals are present togetherwith hydrogen radicals in the plasma atmosphere, the chemical reactionscausing the formation of said semiconductor film are further enhanced.Further, the presence of hydrogen radicals in a controlled amount in theplasma atmosphere formed in the reaction system causes significanteffects such as promoting the chemical reactions causing the formationof said semiconductor film without localization of atoms of theconstituent elements of the film from the raw material gases and toincorporating a desired amount of hydrogen atoms into the film to beformed so that the resulting film has practically applicable desiredcharacteristics. This situation is improved in the case where fluorineradicals are present together with hydrogen radicals in the plasmaatmosphere formed in the reaction system.

It has been found that in the case of a BP film which contains neitherhydrogen atoms nor fluorine atoms or contains hydrogen atoms only in aslight amount or contains both hydrogen atoms and fluorine atoms onlyslight amounts, when it is irradiated with light of a strong intensityfor a long period of time, changes in the film structure or in the filmcomposition due to promotion of by-reactions caused by external factorssuch as dissociation or hydrolysis of the unstable bonds in the film, anincrease in the dangling bonds in the film caused by release of hydrogenatoms and/or fluorine atoms often occurs, thereby causing deteriorationin the initial film structure. However, in the case of thepoly-BP:H(F):M semiconductor film according to the present inventionwhich contains hydrogen atoms in an amount of 0.5 to 7 atomic % andoptionally fluorine atoms in an amount of 0 to 3 atomic %, it has beenconfirmed that these atoms terminate dangling bonds when they arepresent in the crystal grains and also terminate dangling bonds whenthey are present at the grain boundaries and thus the film isaccompanied with an extremely reduced crystal defect level, excellentstructural stress relaxation and excellent electrical, optical andmechanical properties. Thus, the poly-BP:H(F):M semiconductor filmaccording to the present invention can be desirably used as aconstituent element in various electronic devices including photovoltaicdevices.

The n-type poly-BP:H(F):Mn semiconductor film (where Mn is an n-typedopant) according to the present invention contains an n-type dopant(represented by Mn) which is selected from the group consisting of GroupVI A elements, i.e. 0, S, Se and Te. Preferable among these elements areSe and Te.

The p-type poly-BP:H(F):M_(p) semiconductor film (where Mp is a p-typedopant) according to the present invention contains a p-type dopant(represented by M_(p)) which is selected from the group consisting ofGroup II B elements i.e. Zn, Cd and Hg. Preferable among these elementsare Zn and Cd.

As the starting material to impart the n-type dopant to be used in orderto obtain the poly-BP:H(F):Mn semiconductor film, there can bementioned, for example, NO, N₂ O, CO₂, CO, H₂ S, SC1₂, S₂ Cl₂, SOCl₂,SO₂ Cl₂, SeCl₄, Se₂ Cl₂, Se₂ Br₂, SeOCl₂, Se(CH₃)₂, Se(C₂ H₅)₂, TeCl₂,Te(CH₃)₂ and Te(C₂ H₅)₂.

These compounds can be used alone or in combination of two or more ofthem. In the case where the compound is in the liquid state at ordinarytemperatures and at atmospheric pressure, it is desired that thecompound is gasified by feeding an inert gas such as Ar gas or He gasover the liquid compound contained in a bubbling vessel while heatingand the gas generated is introduced into the film-forming chamber. Inthe case where the compound is in the solid state at ordinarytemperatures and at atmospheric pressure, it is desired that thecompound is gasified by passing an inert gas such as Ar gas or He gasover the solid compound contained in a heat sublimation furnace whileheating and the gas generated is introduced into the film-formingchamber.

As the starting material to impart the p-type dopant to be used in orderto obtain the poly-BAs:H(F):M_(p) semiconductor film, there can bementioned, for example, Zn(CH₃)₂, Zn(C₂ H₅)₂, Zn(OCH₃)₂, Zn(OC₂ H₅)₂,Cd(CH₃)₂, Cd(C₂ H₅)₂, Cd(C₃ H₇)₂, Cd(C₄ H₉)₂, Hg(CH₃)₂, Hg(C₂ H₅)₂,Hg(C₆ H₅)₂ and Hg[C.tbd.(C₆ H₅)]₂.

These compounds can be used alone or in combination of two or more ofthem. In the case where the compound is in the liquid state at ordinarytemperatures and at atmospheric pressure, it is desired that thecompound is gasified by feeding an inert gas such as Ar gas or He gasover the liquid compound contained in a bubbling vessel while heatingand the gas generated is introduced into the film-forming chamber.

In the case where the compound is in the solid state at ordinarytemperatures and at atmospheric pressure, it is desired that thecompound is gasified by passing an inert gas such as Ar gas or He gasover the solid compound contained in a heat sublimation furnace whileheating and the gas generated is introduced into the film-formingchamber.

Alternatively, the poly-BP:H(F):Mn semiconductor film or thepoly-BP:H(F):Mp semiconductor film according to the present inventionmay be obtained by substituting part of the boron atoms (B) or part ofthe phosphorous atoms (P) of a poly-BP:H(F) semiconductor film by anelement belonging to Group IV A of the Periodic Table. Specific examplesof such elements are C, Si, Ge, Sn and Pb. Preferable among theseelements are Si, Ge and Sn. That is, in the case where part of the boronatoms (B) of a poly-BP:H(F) semiconductor film is substituted by saidelement, there is afforded an n-type poly-BP:H(F) semiconductor film. Inthe case where part of the phosphorous atoms (P) of the poly-BP:H(F)semiconductor film is substituted by said element, there is afforded ap-type poly-BP:H(F) semiconductor film. It is possible to substituteboth part of the boron atoms and part of the phosphorous atoms by saidelement. In this case, when both parts are equally substituted by saidelement, the resulting semiconductor film sometimes becomes intrinsic.When both parts are substituted by said element, the resulting film willbe of n-type or p-type depending upon which atoms are excessivelysubstituted by said element.

Specific examples of starting materials to impart C are CH₄, C₂ H₆, C₂H₄, C₂ H₂, C₂ H₈, C₃ H₆, C₃ H₄, CF₄, (CF₂)₅, (CF₂)₆, (CF₂)₄, C₂ F₆,CHF₈, CHF₃, CH₂ F₂, CCl₄, (CCl₂)₅, CBr₄, (CBr₂)₅, C₂ Cl₆, C₂ Br₆, CHCl₃,CH₂ Cl₂, CHI₃, CH₂ I₂, C₂ Cl₃ F₃, C₂ H₃ F₃ and C₂ H₂ F₄.

Specific example of starting materials to impart Si are SiH₄, Si₂ H₆,Si₃ H₈, (SiH₂)₄, (SiH₂)₅, (SiH₂)₆, SiF₄, (SiF₂)₅, (SiF₂)₆, (SiF₂)₄, Si₂F₆, Si₃ F₈, SiHF₃, SiH₂ F₂, SiCl₄, (SiCl₂)₅, SiBr₄, (SiBr₂)₅, Si₂ Cl₆,Si₂ Br₆, SiHCl₃, SiH₂ Cl₂, SiHBr₃, SiHI₃, Si₂ Cl₃ F₃, Si₂ H₃ F₂)₅,(GeF₂)₆, (GeF₂)₄, Ge₂ F₆, Ge₃ F₈, GeHF₃, GeH₂ F₂, GeCl₄, (GeCl₂)₅,GeBr₄, (GeBr₂)₅, Ge₂ Cl₆, Ge₂ Br₆, GeHCl₃, GeH₂ Cl₂, GeHBr₃, GeHI₃, Ge₂Cl₃ F₃, Ge₂ H₃ F₃, Ge₂ H₃ Cl₃, Ge₂ H₂ F₄ and Ge₂ H₂ Cl₄.

Specific examples of starting materials to impart Sn are SnH₄, SnCl₄,SnBr₄, Sn(CH₃)₄, Sn(C₂ H₅)₄, Sn(C₃ H₇)₄, Sn(C₄ H₉)₄, Sn(OCH₃)₄, Sn(OC₂H₅)₄, Sn(i--OC₃ H₇)₄ and Sn(t--OC₄ H₉)₄.

Specific examples of starting materials to impart Pb are Pb(CH₃)₄, Pb(C₂H₅)₄ and Pb(C₄ H₉)₄.

As for these compounds, a single compound is generally used. But two ormore compounds can be used together where necessary.

In the case where the compound to be used is in the gaseous state atordinary temperatures and at atmospheric pressure, it is introduced intothe activation space or the film-forming chamber while controlling itsflow rate to a desired value, for example, by means of a mass flowcontroller. In the case where the compound to be used is in the liquidstate at ordinary temperatures and at atmospheric pressure, it isdesired that the liquid compound is gasified by feeding an inert gassuch as Ar gas or He gas into it contained in a bubbling vessel whileheating and the gas generated is introduced into the activation chamberor the film-forming chamber while controlling its flow rate to a desiredvalue. In the case where the compound to be used is in the solid stateat ordinary temperatures and at atmospheric pressure, it is desired thatthe solid compound is gasified by passing an inert gas such as Ar gas orHe gas over it contained in a heat sublimation furnace while heating andthe gas generated is introduced into the activation chamber or thefilm-forming chamber while controlling its flow rate to a desired value.

As the B-containing raw material to be used in any of the foregoingprocesses (1) to (3) in the present invention, there can be mentioned,for example, boron hydrides such as B₂ H₆, B₄ H₁₀, B₅ H₉, B₅ H₁₁, B₆H₁₀, B₆ H₁₂, B₆ H₁₄, etc.; boron halides such as BF₃, BCl₃ and BBr₃ ;alkylated boron compounds such as B(CH₃)₃, B(C₂ H₅)₃, etc.

As for these B-containing raw materials, they can be used alone or incombination of two or more of them.

In the case where the compound to be used is in the gaseous state atordinary temperatures and at atmospheric pressure, it is introduced intothe activation space or the film-forming chamber while controlling itsflow rate to a desired value, for example, by means of a mass flowcontroller. In the case where the compound to be used is in the liquidstate at ordinary temperature and at atmospheric pressure, it is desiredthat the liquid compound is gasified by feeding an inert gas such as Argas or He gas into it contained in a bubbling vessel while heating andthe gas generated is introduced into the activation chamber or thefilm-forming chamber while controlling its flow rate to a desired value.In the case where the compound to be used is in the solid state atordinary temperatures and at atmospheric pressure, it is desired thatthe solid compound is gasified by passing an inert gas such as Ar gas orHe gas over it contained in a heat sublimation furnace while heating andthe gas generated is introduced into the activation chamber or thefilm-forming chamber while controlling its flow rate to a desired value.

As the P-containing raw materials to be used in the present invention,there can be mentioned, for example, PH₃, P₂ H₄, PF₃, PF₅, PCl₃, PCl₅,PBr₃, PBr₅, P(CH₃)₃, P(C₂ H₅)₃, P(C₃ H₇)₃, P(C₄ H₉)₃, P(OCH₃)₃, P(OC₂H₅)₃, P(OC₃ H₇)₃, P(OC₄ H₉)₃, P₂ O₅, POCl₃, PO(OCH₃)₃, PO(OC₂ H₅)₃,PO(OC₃ H₇)₃, PO(OC₄ H₉)₃, etc.

As for these P-containing raw materials, they can be used alone or incombination of two or more of them.

In the case where the compound to be used is in the gaseous state atordinary temperatures and at atmospheric pressure, it is introduced intothe activation space or the film-forming chamber while controlling itsflow rate to a desired value, for example, by means of a mass flowcontroller. In the case where the compound to be used is in the liquidstate at ordinary temperatures and at atmospheric pressure, it isdesired that the liquid compound is gasified by passing an inert gassuch as Ar gas or He gas into it contained in a bubbling vessel whileheating and the gas generated is introduced into the activation chamberor the film-forming chamber while controlling its flow rate to a desiredvalue. In the case where the compound to be used is in the solid stateat ordinary temperatures and at atmospheric pressure, it is desired thatthe solid compound is gasified by passing an inert gas such as Ar gas orHe gas over it contained in a heat sublimation furnace while heating andthe gas generated is introduced into the activation chamber or thefilm-forming chamber while controlling its flow rate to a desired value.

The substrate temperature during forming the foregoing poly-BP:H(F):Msemiconductor film (where M is a dopant of n-type or n-type) by any ofthe foregoing processes (1) to (3) is desired to be controlled to atemperature preferably in the range of from 50° to 600° C., morepreferably in the range of from 50° to 450° C., or most preferably inthe range of from 100° to 400° C.

The inner pressure of the film-forming chamber during forming saidpoly-BP:H(F):M semiconductor film by the foregoing process (1) or theforegoing process (3) is desired to be controlled to a value preferablyin the range of from 1×10⁻⁴ to 50 Torr, more preferably in the range offrom 5×10⁻³ to 10 Torr, or most preferably in the range of from 1×10⁻³to 5 Torr. As for the inner pressure of the film-forming chamber duringforming said poly-BP:H(F):M semiconductor film by the foregoing process(2), it is desired to be controlled to a value preferably in the rangeof from 1×10⁻⁵ to 1×10⁻¹ Torr, more preferably in the range of from1×10⁻⁴ to 1×10⁻² Torr.

In the following, explanation will be given concerning structure of thephotovoltaic element according to the present invention.

When a pin heterojunction photovoltaic element is so designed that thep-type semiconductor layer is made thin so as to impinge light from theside thereof, it can be theoretically expected that the light will beslightly absorbed in the p-type semiconductor layer but mostly absorbedin the i-type semiconductor layer to thereby obtain a desirable current.

However, in practice, there is a limit to how thin the p-typesemiconductor layer can be not only because of the physical andelectrical properties but also because of the film-forming technique. Inview of this, it is commonly required to have a thickness of some tensof angstroms to some hundreds of angstroms and due consideration shouldbe made for its band gap in order to prevent the light impinged frombeing absorbed by the p-type semiconductor layer.

In the case where the i-type semiconductor layer is formed of an a-Si:Hfilm or an a-SiC:H film which is capable of absorbing relatively shortwavelength light and generating photocarriers, absorption of the lightby the p-type semiconductor layer is reduced to provide a symboledimprovement in the current to be outputted. Because of this, it isnecessary for the p-type semiconductor layer to be formed of asemiconductor film having a wide band gap.

In the case of a pin heterojunction photovoltaic element, when itsp-type semiconductor layer or/and its n-type semiconductor layer isformed of a semiconductor film having a wide band gap, it generates ahigh open-circuit voltage (Voc) and exhibits a high photoelectricconversion efficiency.

Thus, as above described, the poly-BP:H(F):M semiconductor film (where Mis a dopant of n-type or p-type) according to the present invention isindeed a desirable semiconductor film of p-type or n-type which can beeffectively used as the p-type semiconductor layer or n-type layer ofthe pin heterojunction photovoltaic element since said semiconductorfilm contains boron atoms (B) and phosphorous atoms (P) uniformlydistributed while satisfying the stoichiometric ratio, hydrogen atoms(H) in a specific amount and optionally fluorine atoms (F) in a specificamount, further contains crystal grains of a desired average size, has adesired crystal orientation, is accompanied with very few defects, has adesirably wide band gap and exhibits symboledly improved characteristicsand thus, it surpasses the known BP semiconductor film.

What has been stated above for the p-type semiconductor layer throughwhich light is impinged is applicable in the case where light isimpinged from the side of the n-type semiconductor layer. Further, inthe case of a multi-cell tandem stacked type or triple type pinheterojunction photovoltaic elements each cell comprising a pin heterojunction photovoltaic element, when the p-type or n-type semiconductorlayer of the cell situated on the side from which light is impinged isformed of the foregoing poly-BP:H(F):M film, symboled effects are alsoprovided.

In addition, the poly-BP:H(F):M semiconductor film according to thepresent invention is capable of also absorbing relatively longwavelength light. Because of this, even in the case where the i-typesemiconductor layer is formed of a-SiGe:H film or uC-Si:H film having anarrow band gap which makes it possible to obtain a large photocurrent,as long as the p-type semiconductor layer through which light isimpinged is formed of the poly-BP:H(F):Mp semiconductor film having awide band gap (where Mp is a p-type dopant) according to the presentinvention, there is desirably caused a so-called back-surface fieldeffect due to a gap of the conduction band between the p-typesemiconductor layer and the i-type semiconductor layer to therebyprevent electrons generated in the i-type semiconductor layer from beingback-diffused at the interface between the p-type semiconductor layerand the i-type semiconductor layer, whereby providing a significantimprovement in the photocurrent to be obtained.

Thus, for the pin heterojunction photovoltaic element, a largephotocurrent is afforded and a symboledly improved photoelectricconversion efficiency is provided. In fact, the pin heterojunctionphotovoltaic element according to the present invention stably providesan excellent photoelectric conversion efficiency not only for a lightsource having a relatively large quantity of short wavelength componentssuch as a fluorescent lamp but also for a light source having a largequantity of long wavelength components such as an incandescent lamp. Inview of this, the pin heterojunction photovoltaic element according tothe present invention can be desirably used also as a power source invarious electric appliances.

Further, the tandem stacked type pin heterojunction photovoltaic elementand the triple type pin heterojunction photovoltaic element according tothe present invention provide excellent photoelectric conversionefficiency, excellent durability and stably exhibit their functionswithout being deteriorated even upon repeated use for a long period oftime and they can be desirably used as solar cells in power supplysystems by sunlight power generation.

The following describes typical examples of the pin heterojunctionphotovoltaic element to be provided according to the present invention.

The following description, however, is not intended to limit the scopeof the present invention.

FIG. 1(A) and FIG. 1(B) schematically show typical embodiments of thepin heterojunction photovoltaic element according to the presentinvention which has a layer structure based on the foregoingpoly-BP:H(F):M semiconductor film.

FIG. 1(A) is a schematic cross-sectional view of a first representativeembodiment of the pin heterojunction photovoltaic element according tothe present invention. In FIG. 1(A), there is shown a pin heterojunctionphotovoltaic element 100 having a structure comprising a lower electrode102, an n type semiconductor layer 103, an i-type semiconductor layer104, a p-type semiconductor layer 105, a transparent electrode 106 and acollecting electrode 107 disposed in this order on a substrate 101.

In the pin heterojunction photovoltaic element shown in FIG. 1(A), lightis impinged from the side of the transparent electrode 106.

FIG. 1(B) is a schematic cross-sectional view of a second representativeembodiment of the pin heterojunction photovoltaic element according tothe present invention.

In FIG. 1(B), there is shown a pin heterojunction photovoltaic element100 comprising a transparent electrode 106, a p-type semiconductor layer105, an i-type semiconductor layer 104, an n-type semiconductor layer103 and a lower electrode 102 disposed in this order on a stransmissivesubstrate 101. In the pin heterojunction photovoltaic element shown inFIG. 1(B), light is impinged from the side of the transmissive substrate101.

For each of the above pin heterojunction photovoltaic elements shown inFIG. 1(A) and FIG. 1(B), it is possible to transpose each of the n-typesemiconductor layer and the p-type semiconductor layer in accordancewith the desired use requirements.

FIG. 1(C) is a schematic cross-sectional view of a representativeembodiment of the triple cell tandem stacked type pinheterorepresentative junction photovoltaic element 120 according to thepresent invention which comprises three cells 111, 112 and 113 stackedon a lower electrode 102 disposed on a substrate 101, each cellcomprising a pin heterojunction photovoltaic element.

The lower cell 111 comprises an n-type semiconductor layer 103, ani-type semiconductor layer 104 and a p-type semiconductor layer 105which are laminated in this order from the side of the substrate 101.The middle cell 112 comprises an n-type semiconductor layer 114, ani-type semiconductor layer 115 and a p-type semiconductor layer 116which are laminated in this order from the side of the substrate 101.

The top cell 113 comprises an n-type semiconductor layer 117, an i-typesemiconductor layer 118 and a p-type semiconductor layer 119 which arelaminated in this order from the side of the substrate 101.

Reference numeral 106 stands for a transparent electrode disposed on thep-type semiconductor layer 119 of the top cell 113. On the transparentelectrode 106, there is provided a collecting electrode 107.

In the triple cell tandem stacked type pin heterojunction photovoltaicelement 120 shown in FIG. 1(C), light is impinged from the side of thetransparent electrode 106.

For this pin heterojunction photovoltaic element, it is also possible totranspose the n-type semiconductor layer and the p-type semiconductorlayer in accordance with the desired use requirements.

Explanation will be made for the substrate, each constituentsemiconductor layer and each constituent electrode in the pinheterojunction photovoltaic element of the present invention.

Substrate

The substrate 101 used in the pin heterojunction photovoltaic elementaccording to the present invention may be of single crystal material ornon-single crystal material. It may be electroconductive or electricallyinsulating, and it may be transparent or opaque. Usable as suchsubstrate are, for example, Fe, Ni, Cr, Al, Mo, Au, Nb, Ta, V, Ti, Pt,and Pb and alloys thereof such as brass and stainless steel. Other thanthese, there can be mentioned films or sheets of synthetic resin such aspolyester, polyethylene, polycarbonate, cellulose acetate,polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene,polyamide, polyimide and the like, and glass or ceramics.

Examples of the substrate comprising a single crystal material are, forexample, wafer-like shaped members obtained by slicing an appropriatesingle crystal of Si, Ge, C, NaCl, KCl, LiF, GaSb, InAs, InSb, GaP, MgO,CaF₂. BaF₂, α-Al₂ O₃ or the like. The surface of any of said wafer-likeshaped members may be provided with an epitaxially grown layer of thesame constituent(s) as the member or of a material whose latticeconstant is close to that of the constituent(s) of the member.

The shape of the substrate may be optionally determined in accordancewith the end use purpose. Examples are plate, belt, drum and suitablelike shapes having a plane or uneven surface. The thickness of thesubstrate is properly determined so that the layer structure of thephotovoltaic member can be formed as desired. In the case whereflexibility is required for the photovoltaic element to be prepared, itcan be made as thin as possible within a range capable of sufficientlyproviding the functions as the substrate. However, the thickness of thesubstrate is usually not less than 10 microns from the view points ofits manufacturing and handling conveniences and its strength.

Electrodes

In the photovoltaic element according to the present invention,appropriate electrodes are used in accordance with the configuration ofthe photovoltaic element to be prepared. As such electrodes, there canbe mentioned the lower electrode, upper electrode (transparentelectrode) and collecting electrode. Said upper electrode denotes theone to be placed at the side on which light is impinged, and said lowerelectrode denotes the one to be placed opposite to the upper electrodethrough the semiconductor layers to be arranged between the twoelectrodes.

These electrodes will be explained in the following.

(i) Lower electrode

For the pin heterojunction photovoltaic element according to the presentinvention, the side through which light is impinged is determineddepending upon whether there is used a transmissive member or an opaquemember as the substrate 101.

In this connection, the position where the lower electrode 102 is to beplaced is properly determined by the kind of substrate 101 to be used.For example, in the case where an opaque member such as a metal memberis used as the substrate 101, light for the generation of aphotoelectromotive force is impinged from the side of the transparentelectrode 106.

Now, in the case where the pin heterojunction photovoltaic element is ofthe configuration as shown in FIG. 1(A) or FIG. 1(C), the lowerelectrode 102 is desired to be placed between the substrate 101 and then-type semiconductor layer 103. In this case, if the substrate 101comprises an electroconductive member, it can function also as the lowerelectrode. However, in the case where the substrate 101 iselectroconductive but is of a high sheet resistance, the lower electrodemay be disposed as a lower resistance electrode serving to output thecurrent or in order to heighten the reflectivity of the incident lightat the surface of the substrate 101 so as to make it utilized moreefficiently.

In the case of FIG. 1(B), there is used a transmissive member as thesubstrate 101 and light is impinged from the side of the substrate 101.In this connection, the lower electrode 102 serving to output a currentis placed on the surface of the top semiconductor layer over above thesubstrate 101. However, in the case where there is used an electricallyinsulating member as the substrate 101 as in the case of 1(B), the lowerelectrode 102 serving to output the current is placed between thesubstrate 101 and the n-type semiconductor layer 103.

The electrode 102 may be a thin film of a metal selected from the groupconsisting of Ag, Au, Pt, Ni, Cr, Cu, Al, Ti, Zn, Mo and W. Saidmetallic thin film may be formed by way of the known vacuum depositiontechnique, electron-beam deposition technique or sputtering technique.However, due consideration should be given that the metallic thin filmto be thus formed is not a resistive component for the photovoltaicelement. In this respect, the metallic thin film constituting theelectrode 102 preferably has a sheet resistance of 50 Ω or less, morepreferably, 10 Ω or less.

In the alternative, it is possible to place a diffusion preventive layercomprising an electroconductive material such as zinc oxide between thelower electrode 102 and the n-type semiconductor layer 103. (This is notshown in the figures.)

In the case where such diffusion preventive layer is used as mentionedabove, the following advantages will be expected: (a) it prevents themetal elements constituting the electrode 102 from diffusing into then-type semiconductor layer 103; (b) being provided with a certainresistance value, it prevents the occurrence of shorts, which wouldotherwise occur between the lower electrode 102 and the transparentelectrode 106 through the semiconductor layers arranged between them dueto pinholes and the like; and (c) it serves to generate multipleinterference effects with the thin film and confine the impinged lightwithin the photovoltaic element.

(ii) Upper electrode (transparent electrode)

The transparent electrode 106 is desired to have a light transmittanceof more than 85% so that it serves to make the semiconductor layerefficiently absorb sunlight or fluorescent light. In addition to this,it is desired to have a sheet resistance of 100 Ω or less from theviewpoint of preventing the internal resistance of the photovoltaicelement from becoming great thereby impairing the performance.

In view of the above, the transparent electrode 106 is desired tocomprise a thin film of a metal oxide selected from the group consistingof SnO₂, In₂ O₃, ZnO, CdO, Cd₂ SnO₂ and ITO (In₂ O₃ +SnO₂) or asemitransparent thin film of a metal selected from the group consistingof Au, Al and Cu.

The transparent electrode 106 is disposed on the p-type semiconductorlayer in the case of the photovoltaic element shown in FIG. 1(A) or FIG.1(C), and it is disposed on the substrate 101 in the case of thephotovoltaic element shown in FIG. 1(B).

In any of these cases, it is necessary to constitute the transparentelectrode 106 with a thin film member selected from the foregoing whichis good in adhesion with the layer or the substrate.

The transparent electrode 106 comprising such thin fill may be formed byway of the known resistance heating deposition technique, electron-beamheating deposition technique, reactive sputtering technique or sprayingtechnique.

(iii) Collecting electrode

The collecting electrode 107 in the photovoltaic element according tothe present invention is disposed on the transparent electrode 106 forthe purpose of reducing the surface resistance of said transparentelectrode..

The collecting electrode 107 is desired to comprise a metallic thin filmof Ag, Cr, Ni, Al, Au, Ti, Pt, Cu, Mo, W or an alloy of these metals. Itis possible for the collecting electrode 107 to be constituted with amember comprising a stacked plurality of such metallic thin films.

The shape and the area of the collecting electrode 107 are properlydesigned so that a sufficient quantity of light can be received by thesemiconductor layer.

Specifically as for the shape, it is desired to be such that it extendsuniformly all over the light receiving face of the photovoltaic element.As for the area, it is desired to cover 15% or less of said lightreceiving face in a preferred embodiment or 10% or less in a morepreferred embodiment.

The member constituting the collecting electrode 107 preferably has asheet resistance of 50 Ω or less, more preferably. 10 Ω or less.

i-type semiconductor layer

In a preferred embodiment, the i-type semiconductor layer in any of thepin heterojunction photovoltaic elements shown in FIGs. 1(A) to 1(C)according to the present invention is formed of a proper i-typenon-single crystal semiconductor film. Preferable as such i-typenonsingle crystal semiconductor film are a-Si:H film, a-Si:F film,a-Si:H:F film, a-SiC:H film, a-SiC:F film, a-siC:H:F film, a-SiGe:Hfilm, a-SiGe:F film, a-SiGe:H:F film, poly-Si:H film, poly-Si:F film andpoly-Si:H:F film.

The pin heterojunction photovoltaic element according present inventionis based on the combined use of the above i-type semiconductor layer andthe p-type or/and n-type semiconductor layer formed of the foregoingpoly-BP:H(F):M semiconductor film and because of this, it provides theforegoing various significant effects.

This situation will be made further apparent from the results obtainedthrough the following experiment.

EXPERIMENT D

There were prepared nineteen pin heterojunction photovoltaic elementsamples (Samples Nos. 91 to 109) of the configuration shown in FIG. 1(B)by using non-single crystal films containing silicon atoms (Si) as amatrix and one or more kinds of atoms selected from the group consistingof hydrogen atoms (H) and fluorine atoms (F) in order to form the i-typeor n-type semiconductor layer; other non-single crystalsilicon-containing films containing neither hydrogen atoms (H) norfluorine atoms (F) in order to form the i-type semiconductor layer; theforegoing poly-BP:H(F):M semiconductor films according to the presentinvention film in order to form the p-type semiconductor layer or/andthe n-type semiconductor layer; and the known BP film in order to formthe p-type semiconductor layer.

In each of the pin heterojunction photovoltaic element samples Nos. 91to 109, as the substrate 101 there was used a quartz glass plate. As thetransparent electrode 106, there was formed a ITO thin film on thesubstrate 101 by means of a conventional reactive sputtering depositiontechnique. As the electrode 102, there was used a Ag thin film formed bya conventional electron-beam deposition technique.

Each of the pin heterojunction photovoltaic element samples Nos. 91 to109 was made such that light is to be impinged from the side of thesubstrate 101.

In the case of the pin heterojunction photovoltaic element sample havingthe p-type semiconductor layer comprised of the foregoingpoly-BP:H(F):Mp semiconductor film according to the present invention,said p-type semiconductor layer was formed by repeating the foregoingprocedures for preparing the film sample No. 76 (by the reactivesputtering method).

Likewise, in the case of the pin heterojunction photovoltaic elementsample having the n-type semiconductor layer comprised of the foregoingpoly-BP:H(F):Mn semiconductor film according to the present invention,said n-type semiconductor layer was formed by repeating the foregoingprocedures for preparing the film sample No. 36 (by the HR-CVD method).

The known i-type semiconductor film, n-type semiconductor film, orp-type semiconductor film in any of the pin heterojunction photovoltaicelements was formed in the known manner.

In the case of the pin heterojunction photovoltaic element sample havingthe p-type semiconductor layer comprised of a known p-type BPsemiconductor film, said p-type semiconductor layer was formed by aconventional sputtering deposition method.

The layer constitution of each of the pin heterojunction photovoltaicelement samples Nos. 91 to 109 prepared was shown in Table 8.

For each of the pin heterojunction photovoltaic element samples Nos. 91to 109 thus obtained, there were evaluated a short-circuit current (Isc)under irradiation of AM-1 light (100 mW/cm²) and an open-circuit voltage(Voc).

The results obtained are collectively shown in Table 8.

From the results obtained through the experiment, the following findingshave been obtained. That is, it has been found that in each of the cases(Samples Nos. 91-93 and 97-99) where the n-type and i-type layers areformed of the same kind of a semiconductor film and the p-type layer isformed of the poly-BP:H(F):Mp semiconductor film according to thepresent invention, the Isc and the Voc exhibited surpass those exhibitedby any of the pin heterojunction photovoltaic elements (Samples Nos.104-109) in which the p-type semiconductor layer is formed of the knownp-type BP semiconductor film, and the n-type and i-type semiconductorlayers are formed of those silicon-containing non-single crystalsemiconductor films used in Samples Nos. 91-99. It has been also foundthat in any of the cases (Samples Nos. 94-96) where the p-type andn-type semiconductor layers are formed of the poly-BP:H(F):Msemiconductor film according to the present invention and the i-typesemiconductor layer is formed of a a-Si:H film, a-Si:F film or a-Si:H:Ffilm, the Voc is markedly improved.

On the other hand, in each of the cases (Samples Nos. 100-103) in whichthe p-type semiconductor layer is formed of the poly-BP:H(F):Mpsemiconductor film, the n-type semiconductor layer is formed of ann-type a-Si:H film, and the i-type semiconductor layer is formed of ana-Si film, a-SiC film, a-SiGe film or poly-Si film, it has been foundthat there are not provided desirable Isc and Voc and thus, each of themis not practically acceptable.

In view of the above, it has been recognized that for the pinheterojunction photovoltaic element according to the present invention,it is necessary for the i-type semiconductor layer to be formed of asilicon-containing semiconductor film containing hydrogen atoms (H)or/and fluorine atoms (F) selected from the group consisting of a-Si:Hfilm, a-Si:F film, a-Si:H:F film, a-SiC:H film, a-SiC:F film, a-SiC:H:Ffilm, a-SiGe:H film, a-SiGe:F film, a-SiGe:H:F film, poly-Si:H film,poly-Si:F film and poly-Si:H:F film.

In order to form a desirable pin heterojunction in the preparation ofthe pin heterojunction photovoltaic element according to the presentinvention, it is desired to continuously form the n-type semiconductorlayer, the i-type semiconductor layer and the p-type semiconductor layerunder an enclosed vacuum condition. In a preferred embodiment in thisrespect, the formation of said pin heterojunction is carried out in asingle film-forming apparatus. In the alternative, it is possible toform one semiconductor layer in a film-forming apparatus, to transferthe substrate having the semiconductor layer formed thereon through agate valve into an other film-forming apparatus and to form a successivesemiconductor layer on the previously formed semiconductor layertherein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described more specifically whilereferring to Examples, but the present invention is not intended tolimit the scope only to these examples.

EXAMPLE 1

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A) by the foregoing process (1) (HR-CVDmethod) to be practiced in the HR-CVD apparatus shown in FIG. 2 in thefollowing way.

As the substrate 101, there was used a stainless steel plate of 50 mm by50 mm in size.

Firstly, the substrate was placed in a known sputtering apparatus (notshown). The sputtering apparatus was evacuated to a vacuum of about1×10⁻⁵ Torr or below. On the substrate was deposited a Ag thin film ofabout 1000 Å in thickness as the lower electrode 102 by sputtering Ag inAr gas. The substrate was taken out from the sputtering apparatus andthen fixed, with the lower electrode 102 facing downward, onto thesubstrate holder 202 on the substrate transfer unit 206 positioned inthe load lock chamber 212. The load lock chamber 212 was evacuated to10⁻⁵ Torr or below by means of a vacuum pump (not shown). Duringevacuation, the film-forming chamber 201 was evacuated to 10⁻⁵ Torr orbelow by means of the vacuum pump 221. When the pressures in the twochambers became almost balanced, the two chambers were opened and thesubstrate transfer unit 206 was moved through the gate valve 207 to thefilm forming chamber 201. Then, the gate valve 207 was closed. Thesubstrate (203 in FIG. 2) was heated to 220° C. by actuating the heater205 and it was maintained at this temperature. Thereafter, Si₂ F₆ gasand PH₃ gas diluted SiF₄ gas to 4000 ppm (hereinafter referred to as"PH₃ /SiF₄ gas") were introduced through the gas supply pipe 214 intothe activation chamber 208 maintained at 700° C. by the activationenergy generation means 211 at respective flow rates of 25 sccm and 10sccm while being mixed. At the same time, He gas and H₂ gas wereintroduced through the gas supply pipe 215 into the activation chamber209 at respective flow rates of 100 sccm and 50 sccm while being mixed.The inner pressure of the film-forming chamber 201 was kept at 0.3 Torrby regulating the exhaust valve 220. Film-forming was started byapplying microwave power (2.45 GHz) of 300 W from the activation energygeneration means 212 into the activation chamber 209. Precursorsgenerated in the activation chamber 208 and hydrogen radicals generatedin the activation chamber 209 were successively transported respectivelythrough the transport conduits 217 and 218 into the film-forming chamber201, where they were chemically reacted to form a 400 Å thick n-typea-Si:H:F:P semiconductor film as the n-type semiconductor layer 103 onthe Ag thin film as the lower electrode 102. The application ofmicrowave power and the introduction of gases were suspended, and thefilm-forming chamber 201 was evacuated to 10⁻⁵ Torr or below by thevacuum pump.

Then, the substrate (203) was moved through the gate valve 207 into thefilm-forming chamber 222 having the same constitution as that of thefilm-forming chamber 201 which had been evacuated to 10⁻⁵ Torr or belowby means of the substrate transfer unit 206. Then, the abovefilm-forming procedures were repeated, except that only Si₂ F₆ gas wasintroduced at a flow rate of 30 sccm without using the PH₃ /SiF₄ gas andthe microwave power was changed to 400 W, to thereby form a 3500 Å thicknon-doped a-Si:H:F film as the i-type semiconductor layer 104 on thepreviously formed n-type semiconductor layer 103.

The application of microwave power and the introduction of gases weresuspended, and the film-forming chamber 222 was evacuated to 10⁻⁵ Torror below. Then, the substrate (203) was moved through the gate valveinto a film-forming chamber (not shown) have the same constitution asthat of the film-forming chamber 201 which had been evacuated to 10⁻⁵Torr or below.

Then, a liquid mixture composed of B(C₂ H₅)₃ and Zn(CH₃)₂ with thequantitative ratio of 10⁴ :1 in a bubbling vessel (not shown) wasgasified by bubbling it with He gas (as a carrier gas) supplied at aflow rate of 20 sccm to generate a raw material gas containing said twocompounds. The resultant raw material gas was successively introducedthrough the ga supply pipe 214 into the activation chamber 208 at a flowrate of 2.5×10⁻⁴ mol/min, into which microwave power (2.45 GHz) of 60 Wfrom the activation energy generation means 211 was applied. At the sametime, PF₅ gas was introduced at a flow rate of 5.5 through the gassupply pipe 216 into the activation chamber 210 maintained at 500° C. bythe activation energy generation means 213. Concurrently, H₂ gas and Hegas were introduced through the gas supply pipe 215 into the activationchamber 209 at respective flow rates of 8 sccm and 40 sccm while beingmixed, into which microwave power (2.45 GHz) of 320 W from theactivation energy generation means 212 was applied. At this time, theinner pressure of the film-forming chamber was controlled to 60 m Torr.Precursors generated in the activation chamber 208, other precursorsgenerated in the activation chamber 210 and hydrogen radicals generatedin the activation chamber 209 were successively introduced into thefilm-forming chamber respectively through the transport conduits 217,219 and 218, where they were chemically reacted to form a 200 Å thickp-type poly-BP:H:F:Zn semiconductor film as the p-type semiconductorlayer 105 on the previously formed i-type semiconductor layer on thesubstrate maintained at 210° C., the substrate being placed at aposition 8 cm distant from the outlet of the transportation conduit 218.

Thereafter, the substrate transfer unit was moved to the load lockchamber through the gate valve. After cooling therein, the substrate onwhich were deposited the n-type, i-type and p-type semiconductor layerswas taken out. Then, the substrate was placed in a known vacuumdeposition apparatus, which was evacuated to 10⁻⁵ Torr or below. On theforegoing p-type semiconductor layer 105 on the substrate was depositedan ITO thin film of about 700 Å in thickness in an oxygen atmosphere atabout 1×10⁻³ Torr. The source of deposition was a 1:1 (by weight)mixture of In and Sn placed in a crucible which was heated by theresistance heating method. The substrate temperature was 170° C. In thisway the transparent electrode 106 was formed. After cooling, thesubstrate was removed. With a permalloy mask placed on the transparentelectrode 106, the substrate was placed in another known vacuumdeposition apparatus, which was evacuated to 1×10⁻⁵ Torr or below. An Agthin film of about 0.8 μm in thickness was deposited by the resistanceheating method to form an about 0.8 pm thick comb-shaped collectingelectrode 107. Thus there was obtained Element Sample No. 1. Thecharacteristics of Element Sample No. 1 as a solar cell were evaluatedin the following manner.

The open-circuit voltage (Voc) and the short-circuit current (Isc) whichare produced when the transparent electrode is irradiated with AM-1light (100 mW/cm²) were measured. The relative value of output obtainedwhen AM-1 light is irradiated through an interference filter of 400 nmwas also measured. Said relative value is a value obtained when thevalue obtained when the comparative element sample prepared in the laterdescribed Comparative Example 1 was measured under the same condition asin the above was made to be the control (1).

The measured results are shown in Table 9.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 9.

EXAMPLE 2

There was prepared a pin heterojunction photovoltaic element (ElementSample No. 2) of the configuration shown in FIG. 1(A) by repeating theprocedures of Example 1, except that the p-type semiconductor layer 105was formed by the foregoing process (2) (reactive sputtering method)practiced in the reactive sputtering apparatus shown in FIG. 3 in thefollowing manner.

That is, the substrate having the lower electrode 102, the n-typesemiconductor layer 103 and the i-type semiconductor layer 104 thereonwhich were formed respectively in the same manner as in Example 1 wasmoved by the substrate transfer unit into the other film-forming chambercomprising the reactive sputtering film-forming chamber 301 shown inFIG. 3. The film-forming chamber 301 was evacuated to 1 ×10⁻⁵ Torr orbelow. The substrate was heated to 220° C. by actuating the heater 306and it was maintained at this temperature. Film-forming was conductedunder the conditions shown in Table 10 to thereby form a 200 Å thickp-type poly-BP:H:F:Zn semiconductor film as the p-type semiconductorlayer 105 on the previously formed i-type semiconductor layer 104.Thereafter, the substrate was moved to the load lock chamber and it wascooled therein.

The substrate was taken therefrom, and on the foregoing p-typesemiconductor layer 105 was formed an about 700 Å thick ITO film as thetransparent electrode 106 and then an about 0.8 μm thick comb-shapedcollecting electrode 107 comprising a 0.8 μm thick Ag thin film in thesame manner as in Example 1.

Thus there was obtained Element Sample No. 2.

The characteristics of Element Sample No. 2 as a solar cell wereevaluated in the same manner as in Example 1.

The results obtained are shown in Table 9.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 9.

EXAMPLE 3

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 3) by repeating theprocedures of Example 1, except that the p-type semiconductor layer 105was formed by the foregoing process (3)(plasma CVD method) practiced inthe plasma CVD apparatus shown in FIG. 4 in the following manner.

That is, the substrate having the lower electrode 102, the n-typesemiconductor layer 103 and the i-type semiconductor layer 104 thereonwhich were formed respectively in the same manner as in Example 1 wasmoved by the substrate transfer unit into the other film-forming chambercomprising the plasma CVD film-forming chamber 401 shown in FIG. 4. Thefilm-forming chamber 401 was evacuated to 1 x×10⁻⁵ or below. Thesubstrate was heated to 230° C. by the heater 405 and it was maintainedat this temperature. Then, raw material gas (A), raw material gas (B)and raw material gas (C) shown in Table 11 were introduced through therespective gas supply pipes 408 and 409 into the film-forming chamber401 under the respective conditions shown in Table 11. The innerpressure of the film-forming chamber 401 was controlled to andmaintained at 0.8 Torr by regulating the exhaust valve 414 and whilemonitoring by the pressure gage 417. High frequency power (13.56 MHz) of70 W from the high frequency power source 410 was applied through thecathode 412 into the film-forming chamber 401 to thereby form a 200 Åthick p-type poly-BP:H:F:Zn semiconductor film as the p-typesemiconductor layer 105 on the previously formed i-type semiconductorlayer. Thereafter, the substrate transfer unit was moved to the loadlock chamber and it was cooled therein.

The substrate was taken out therefrom, and on the foregoing p-typesemiconductor layer 105 was formed an about 700 Å thick ITO film as thetransparent electrode 106 and then an about 0.8 μm thick comb-shapedcollecting electrode 107 comprising an 0.8 μm thick Ag thin film in thesame manner as in Example 1.

Thus there was obtained Element Sample No. 3.

The characteristics of Element Sample No. 3 as a solar cell wereevaluated in the same manner as in Example 1. The results obtained areshown in Table 9.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film wa examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 9.

EXAMPLE 4

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 4) by repeating theprocedures of Example 1, except that the i-type semiconductor layer 104was formed of a non-doped i-type a-SiC:H:F film which was prepared inthe following manner.

That is, after the n-type semiconductor layer 103 was formed, thesubstrate was moved by the substrate transfer unit through the gatevalve to the other film-forming chamber having the same constitution asthat of the film-forming chamber 201.

The gate valve was closed and the film-forming chamber was evacuated toand maintained at 1×10⁻⁵ Torr or below. The substrate was then heated to220° C. by actuating the heater 205 and it was maintained at thistemperature. Thereafter, raw material gas (A), raw material gas (B) andraw material gas (C) shown in Table 12 were introduced into therespective activation chambers 208, 209 and 210, wherein they wereseparately activated under the respective activation conditions shown inTable 12 to generate respective active species. The respective activespecies were separately introduced through the respective transportconduits 217, 218 and 219 into the film-forming chamber, wherein theywere chemically reacted to form a 3500 Å thick non-doped i-typea-SiC:H:F film as the i-type semiconductor layer 104 on the previouslyformed n-type semiconductor layer 103 comprising a 400 Å thick n-typea-Si:H:F: semiconductor film.

On the thus formed i-type semiconductor layer 104 was formed a 200 Åthick p-type poly-BP:H:F:Zn semiconductor film as the p-typesemiconductor layer 105 in the same manner as in Example 1. Thereafter,the substrate transfer unit was moved to the load lock chamber and itwas cooled therein.

The substrate was taken out therefrom, and on the foregoing p-typesemiconductor layer 105 was formed an about 700 Å thick ITO film as thetransparent electrode 106 and then an about 0.8 μm thick comb-shapedcollecting electrode 107 comprising an 0.8 μm thick Ag thin film in thesame manner as in Example 1.

Thus there was obtained Element Sample No. 4.

The characteristics of Element Sample No. 4 as a solar cell wereevaluated in the same manner as in Example 1. The results obtained areshown in Table 9.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results were shown in Table 9.

EXAMPLE 5

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 5) by repeating theprocedures of Example 1, except that the i-type semiconductor layer 104was formed of a non-doped i-type a-SiGe:H:F film which was prepared inthe following manner.

That is, after the n-type semiconductor layer 103 was formed, thesubstrate was moved by the substrate transfer unit through the gatevalve to the other film-forming chamber having the same constitution asthat of the film-forming chamber 201.

The gate valve was closed and the film-forming chamber was evacuated toand maintained at 1×10⁻⁵ Torr or below. The substrate was then heated to220° C. by actuating the heater 205 and it was maintained at thistemperature. Thereafter, raw material gas (A), raw material gas (B) andraw material gas (C) shown in Table 13 were introduced into therespective activation chambers 208, 209 and 210, wherein they wereseparately activated under the respective activation conditions shown inTable 13 to generate respective active species. The respective activespecies were separately introduced through the respective transportconduits 217, 218 and 219 into the film-forming chamber, wherein theywere chemically reacted to form a 3500 Å thick non-doped i-typea-SiGe:H:F film as the i-type semiconductor layer 104 on the previouslyformed n-type semiconductor layer 103 comprising a 400 Å thick n-typea-Si:H:F:P semiconductor film.

On the thus formed i-type semiconductor layer 104 was formed a 200 Åthick p-type poly-BP:H:F:Zn semiconductor film as the p-typesemiconductor layer 105 in the same manner as in Example 1. Thereafter,the substrate transfer unit was moved to the load lock chamber and itwas cooled therein.

The substrate was taken out therefrom, and on the foregoing p-typesemiconductor layer 105 was formed an about 700 Å thick ITO film as thetransparent electrode 106 and then an about 0.8 μm thick comb-shapedcollecting electrode 107 comprising an 0.8 μm thick Ag thin film in thesame manner as in Example 1.

Thus there was obtained Element Sample No. 5.

The characteristics of Element Sample No. 5 as a solar cell wereevaluated in the same manner as in Example 1. The results obtained areshown in Table 9.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 9.

EXAMPLE 6

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 6) by repeating theprocedures of Example 1, except that the i-type semiconductor layer 104was formed of a non-doped i-type poly-Si:H:F film which was prepared inthe following manner.

That is, after the n-type semiconductor layer 103 was formed, thesubstrate was moved by the substrate transfer unit through the gatevalve to the other film-forming chamber having the same constitution asthat of the film-forming chamber 201.

The gate valve was closed and the film-forming chamber was evacuated toand maintained at 1×10⁻⁵ Torr or below. The substrate was then heated to220° C. by actuating the heater 205 and it was maintained at thistemperature.

Thereafter, raw material gas (A) and raw material gas (B) shown in Table14 were introduced into the respective activation chambers 208 and 209,wherein they were separately activated under the respective activationconditions shown in Table 14 to generate respective active species. Therespective active species were separately introduced through therespective transport conduits 217 and 218 into the film-forming chamber,wherein they were chemically reacted to form a 8000 Å thick non-dopedi-type poly-Si:H:F film as the i-type semiconductor layer 104 on thepreviously formed n-type semiconductor layer comprising a 400 Å thickn-type a-Si:H:F:P semiconductor film.

On the thus formed i-type semiconductor layer 104 was formed a 200 Åthick p-type poly-BP:H:F:Zn semiconductor film as the p-typesemiconductor layer 105 in the same manner as in Example 1. Thereafter,the substrate transfer unit was moved to the load lock chamber and itwas cooled therein.

The substrate was taken out therefrom, and on the foregoing p-typesemiconductor layer 105 was formed an about 700 Å thick ITO film as thetransparent electrode 106 and then an about 0.8 μm thick comb-shapedcollecting electrode 107 comprising an 0.8 μm thick Ag thin film in thesame manner as in Example 1.

Thus there was obtained Element Sample No. 6.

The characteristics of Element Sample No. 6 as a solar cell wereevaluated in the same manner as in Example 1. The results obtained areshown in Table 9.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 9.

EXAMPLE 7

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(B)(Element Sample No. 7) in accordancewith the manner of Example 1.

That is, as the substrate 101, there was used a Corning glass plate No.7059 of 50 mm by 50 mm in size. On the substrate was formed an ITO thinfilm of about 500 Å in thickness as the transparent electrode 106 by theresistance heating method. The procedures of forming the p-typesemiconductor layer in Example 1 were repeated to form a 200 Å thickp-type poly-BP:H:F:Zn semiconductor film as the p-type semiconductorlayer 105 on the transparent electrode. Then, the procedures for formingthe i-type semiconductor layer in Example 1 were repeated to form a 3500Å thick non-doped i-type a-Si:H:F film as the i-type semiconductor layer104 on the p-type semiconductor layer. Successively, there was formed a400 Å thick n-type a-Si:H:F:P semiconductor film as the n-typesemiconductor layer 103 on the i-type semiconductor layer 104 byrepeating the procedures of forming the n-type semiconductor layer inExample 1. On this n-type semiconductor was formed a 0.5 μm thickelectrode comprising a 0.5 μm thick Ag film as the electrode 102 byrepeating the procedures of forming the comb-shaped collecting electrodein Example 1. Thus there was obtained Element Sample No. 7. Thecharacteristics of Element manner as in Example 1.

The results obtained are shown in Table 9.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for the hydrogen content, fluorinecontent, and the average size of crystal grains in the film in the samemanner as above described.

The results are shown in Table 9.

EXAMPLE 8

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 8) by repeating theprocedures of Example 1, except that the n-type semiconductor layer 104was formed of an n-type poly-BAs:H:F:Se semiconductor film which wasprepared in the following manner.

That is, after the lower electrode 102 was formed, the substrate wasmoved by the substrate transfer unit through the gate valve to the otherfilm-forming chamber having the same constitution as that of thefilm-forming chamber 201.

The gate valve was closed and the film-forming chamber was evacuated toand maintained at 1×10⁻⁵ Torr or below. The substrate was then heated to220° C. by actuating the heater 205 and it was maintained at thistemperature. Then, liquid mixture composed of B(CH₃)₂ and Se(CH₃)₂ withthe quantitative ratio of 104:1 in a bubbling vessel (not shown) wasgasified by bubbling it with He gas (as a carrier gas) supplied at aflow rate of 10 sccm to generate a raw material gas containing the twocompounds. The resultant raw material gas was successively introducedthrough the gas supply pipe 214 into the activation chamber 208 at aflow rate of 4.0×10⁻⁴ mol/min

High frequency power (13.56 MHz) of 100 W from the activation energygeneration means 211 was applied into the activation chamber 208 togenerate precursors which were successively introduced through thetransport conduit 217 into the film-forming chamber 201. At the sametime, PF₅ gas was introduced through the gas supply pipe 216 into theactivation chamber 210 maintained at 500° C. by the activation energygeneration means 213 at a flow rate of 5 sccm, to thereby generateprecursors containing fluorine radicals, which were successivelyintroduced through the transport conduit 219 into the film-formingchamber 201. Concurrently, H₂ gas and He gas were introduced through thegas supply pipe 215 into the activation chamber 209 at respective flowrates of 6 sccm and 60 sccm while being mixed, into which microwavepower (2.45 GHz) of 50 W from the activation energy generation means 212was applied to generate hydrogen radicals, which were successivelyintroduced through the transport conduit 218 (the outlet of which is 7cm distant from the substrate) into the film-forming chamber 201.

At this time, the inner pressure was maintained at 0.8 Torr.

The foregoing precursors and hydrogen radicals thus introduced into thefilm-forming chamber 201 were chemically reacted to form a 400 Å thickn-type poly-BP:H:F:Se semiconductor film as the n-type semiconductorlayer 103 on the lower electrode 102. The film-forming conditions usedin this case are shown in Table 15.

On this n-type semiconductor layer was formed a 3500 Å thick non-dopedi-type a-Si:H:F film as the i-type semiconductor layer 104 by repeatingthe procedures of forming the i-type semiconductor layer in Example 1.Then, on this i-type semiconductor layer was formed a 200 Å thick p-typepoly-BP:H:F:Zn semiconductor film as the p-type semiconductor layer 105by repeating the procedures of forming the p-type semiconductor layer inExample 1. On this p-type semiconductor layer were successively formed a700 Å thick ITO film as the transparent electrode 106 and an 0.8 μmthick comb-shaped film comprising an 0.8 μm thick Ag film as thecollecting electrode 107 respectively in the same manner as in Example1.

Thus there was obtained Element Sample No. 8.

The characteristics of Element Sample No. 8 as a solar cell wereevaluated in the same manner as in Example 1.

The results obtained are shown in Table 9.

Besides the foregoing, using two quartz glass plates, there were formedan n-type poly-BP:H:F:Se semiconductor film and a p-type poly-BP:H:F:Znsemiconductor film separately by repeating the foregoing procedures forthe formation of the n-type semiconductor layer 103 and the formation ofthe p-type semiconductor layer 105.

Each of the resultant films was examined for hydrogen content, fluorinecontent, and the average size of crystal grains in the film in the samemanner as above described.

The results are shown in Table 9.

EXAMPLE 9

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 9) by repeating theprocedures of Example 1, except that the n-type semiconductor layer 103was formed of a 400 6521 thick n-type BP:Se semiconductor which wasprepared in accordance with a known sputtering method under theconditions shown in Table 16.

The characteristics of Element Sample No. 9 as a solar cell wereevaluated in the same manner as in Example 1.

The results obtained are shown in Table 17.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedure for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 17.

EXAMPLE 10

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 10) by repeating theprocedures of Example 1, except that the n-type semiconductor layer 103was formed of a 400 Å thick n-type a-SiGe:H:F:P semiconductor film whichwas prepared by the foregoing process (3) by the plasma CVD method to bepracticed in the plasma CVD apparatus shown in FIG. 4 under theconditions shown in Table 18.

The characteristics of Element Sample 10 as a solar cell are evaluatedin the same manner as in Example 1.

The results obtained are shown in Table 17.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 17.

EXAMPLE 11

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 11) by repeating theprocedures of Example 1, except that the n-type semiconductor layer 103was formed of a 400 Å thick n-type a-SiC:H:F:P semiconductor film whichwas prepared by the foregoing process (3) by the plasma CVD methodpracticed in the plasma CVD apparatus shown in FIG. 4 under theconditions shown in Table 19.

The characteristics of Element Sample 11 as a solar cell are evaluatedin the same manner as in Example 1.

The results obtained are shown in Table 17.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 17.

EXAMPLE 12

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 12) by repeating theprocedures of Example 1, except that the n-type semiconductor layer 103was formed of a 400 Å thick n-type GaAs:Si semiconductor film which wasprepared by the foregoing process (2) by the reactive sputtering methodpracticed in the reactive sputtering apparatus shown in FIG. 3 under theconditions shown in Table 20.

The characteristics of Element Sample 12 as a solar cell are evaluatedin the same manner as in Example 1.

The results obtained are shown in Table 17.

Besides the foregoing, using a quartz glass plate, there was formed ap-type poly-BP:H:F:Zn semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 17.

EXAMPLE 13

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 13) by repeating theprocedures of Example 8, except that the i-type semiconductor layer 104was formed of a 3500 Å thick non-doped i-type a-Si:H semiconductor filmwhich was prepared by the foregoing process (3) by the plasma CVD methodto be practiced in the plasma CVD apparatus shown in FIG. 4 under theconditions shown in Table 21.

The characteristics of Element Sample 13 as a solar cell are evaluatedin the same manner as in Example 1.

The results obtained are shown in Table 17.

Besides, the foregoing, using two quartz glass plates, there are formedan n-type poly-BP:H:F:Se semiconductor film and p-type poly-BP:H:F:Znsemiconductor film separately by repeating the foregoing procedures forthe formation of the n-type semiconductor layer 103 and the formation ofthe p-type semiconductor layer 105.

Each of the resultant films was examined for hydrogen content, fluorinecontent, and the average size of crystal grains in the film in the samemanner as above described.

The results are shown in Table 17.

EXAMPLE 14

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 14) by repeating theprocedures of Example 8, except that the i-type semiconductor layer 104was formed of a 3500 Å thick non-doped i-type a-SiGe:H semiconductorfilm which was prepared by the foregoing process (3) by the plasma CVDmethod practiced in the plasma CVD apparatus shown in FIG. 4 under theconditions shown in Table 22.

The characteristics of Element Sample 14 as a solar cell are evaluatedin the same manner as in Example 1.

The results obtained are shown in Table 17.

Besides the foregoing, using two quartz glass plates, there are formedan n-type poly-BP:H:F:Se semiconductor film and a p-type poly-BP:H:F:Znsemiconductor film separately by repeating the foregoing procedures forthe formation of the n-type semiconductor layer 103 and the formation ofthe p-type semiconductor layer 105.

Each of the resultant films was examined for hydrogen content, fluorinecontent, and the average size of crystal grains in the film in the samemanner as above described.

The results are shown in Table 17.

EXAMPLE 15

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 15) by repeating theprocedures of Example 8, except that the i-type semiconductor layer 104was formed of a 3500 Å thick non-doped i-type a-SiC:H semiconductor filmwhich was prepared by the foregoing process (3) by the plasma CVD methodpracticed in the plasma CVD apparatus shown in FIG. 4 under theconditions shown in Table 23.

The characteristics of Element Sample 15 as a solar cell are evaluatedin the same manner as in Example 1.

The results obtained are shown in Table 17.

Besides the foregoing, using two quartz glass plates there are formed ann-type poly-BP:H:F:Se semiconductor film and a p-type poly-BP:H:F:Znsemiconductor film separately by repeating the foregoing procedures forthe formation of the n-type semiconductor layer 103 and the formation ofthe p-type semiconductor layer 105.

Each of the resultant films was examined for hydrogen content, fluorinecontent, and the average size of crystal grains in the film in the samemanner as above described.

The results are shown in Table 17.

EXAMPLE 16

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 16) by repeating theprocedures of Example 8, except that the i-type semiconductor layer 104was formed of a 3500 Å thick non-doped i-type a-Si:F semiconductor filmwhich was prepared by the foregoing process (2) by the the reactivesputtering method practiced in the plasma CVD apparatus shown in FIG. 3under the conditions shown in Table 24.

The characteristics of Element Sample 16 as a solar cell are evaluatedin the same manner as in Example 1.

The results obtained are shown in Table 17.

Besides the foregoing, using two quartz glassplates, there are formed ann-type poly-BP:H:F:Se semiconductor film and a p-type poly-BP:H:F:Znsemiconductor film separately by repeating the foregoing procedures forthe formation of the n-type semiconductor layer 103 and the formation ofthe p-type semiconductor layer 105.

Each of the resultant films was examined for hydrogen content, fluorinecontent, and the average size of crystal grains in the film in the samemanner as above described.

The results are shown in Table 17.

EXAMPLE 17

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 17) by repeating theprocedures of Example 8, except that the i-type semiconductor layer 104was formed of a 3500 6521 thick non-doped i-type a-Si:GeC:Hsemiconductor film which was prepared by the foregoing process (3) bythe the reactive sputtering method practiced in the reactive sputteringapparatus shown in FIG. 3 under the conditions shown in Table 25.

The characteristics of Element Sample 17 as a solar cell are evaluatedin the same manner as in Example 1.

The results obtained are shown in Table 17.

Besides the foregoing, using two quartz glassplates, there are formed ann-type poly-BP:H:F:Se semiconductor film and a p-type poly-BP:H:F:Znsemiconductor film separately by repeating the foregoing procedures forthe formation of the n-type semiconductor layer 103 and the formation ofthe p-type semiconductor layer 105.

Each of the resultant films wa examined for hydrogen content, fluorinecontent, and the average size of crystal grains in the film in the samemanner as above described.

The results are shown in Table 17.

EXAMPLE 18

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(A)(Element Sample No. 18) by repeating theprocedures of Example 8, except that the i-type semiconductor layer 104was formed of a 3500 Å thick non-doped i-type poly-Si:H semiconductorfilm which was prepared by the foregoing process (2) by the the reactivesputtering method practiced in the reactive sputtering apparatus shownin FIG. 3 under the conditions shown in Table 26.

The characteristics of Element Sample 18 as a solar cell are evaluatedin the same manner as in Example 1.

The results obtained are shown in Table 17.

Besides the foregoing, using two quartz glassplates, there are formed ann-type poly-BP:H:F:Se semiconductor film and a p-type poly-BP:H:F:Znsemiconductor film separately by repeating the foregoing procedures forthe formation of the n-type semiconductor layer 103 and the formation ofthe p-type semiconductor layer 105.

Each of the resultant films was examined for hydrogen content, fluorinecontent, and the average size of crystal grains in the film in the samemanner as above described.

The results are shown in Table 17.

EXAMPLE 19

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(B)(Element Sample No. 19) in accordancewith the manner of Example 1 and the manner of Example 1.

That is, as the substrate 101, there was used a Corning glass plate No.7059 of 50 mm by 50 mm in size. On the substrate an ITO thin film ofabout 500 Å in thickness as the transparent electrode 106 was formed bythe resistance heating method.

On the foregoing transparent electrode was formed a 200 Å thick p-typea-Si:H:F:B semiconductor film as the p-type semiconductor layer 105 byrepeating the procedures of forming the n-type layer in Example 1,except that BF₃ gas diluted with H₂ gas to 4000 ppm (BF₃ /H₂ gas) wasintroduced into the film-forming chamber at a flow rate of 35 sccm instead of the PH₃ /SiF₄ gas. On this p-type semiconductor layer wasformed a 3500 Å thick non-doped i-type a-Si:H:F film as the i-typesemiconductor layer 104 by repeating the procedures of forming thei-type semiconductor layer in Example 1. There was then formed a 400 Åthick n-type poly-BP:H:F:Se semiconductor film as the n-typesemiconductor layer 103 on the i-type semiconductor layer 104 byrepeating the procedures of forming the n-type semiconductor layer inExample 8. On this n-type semiconductor was formed a 0.5 μm thick Agfilm as the electrode 102. Thus there was obtained Element Sample No.19. The characteristics of Element Sample No. 19 as a solar cell areevaluated in the same manner as in Example 1.

The results obtained are shown in Table 27.

Besides the foregoing, using a quartz glass plate, there was formed ann-type poly-BP:H:F:Se semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the n-typesemiconductor layer 103.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 27.

EXAMPLE 20

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(B)(Element Sample No. 20) basically inaccordance with the manner of Example 8.

That is, as the substrate 101, there was used a Corning glass plate No.7059 of 50 mm by 50 mm in size. On the substrate an ITO thin film ofabout 500 Å in thickness as the transparent electrode 106 was formed bythe resistance heating method. The procedures of forming the n-typesemiconductor layer in Example 11 are repeated to form a 200 Å thickp-type a-SiC:H:F:B semiconductor film as the p-type semiconductor layer105 on the transparent electrode, except that BF₃ gas diluted with H₂gas to 4000 ppm (BF₃ /H₂ gas) was introduced into the film-formingchamber at a flow rate of 30 sccm instead of the PH₃ /H₂ gas. Then, theprocedures for forming the i-type semiconductor layer in Example 1 arerepeated to form a 3500 Å thick non-doped i-type a-Si:H:F film as thei-type semiconductor layer 104 on the p-type semiconductor layer.Successively, there was formed a 400 Å thick n-type poly-BP:H:F:Sesemiconductor film as the n-type semiconductor layer 103 on the i-typesemiconductor layer 104 by repeating the procedures of forming then-type semiconductor layer in Example 8. On this n-type semiconductorwas formed a 0.5 μm thick Ag film as the electrode 102. Thus there wasobtained Element Sample No. 20. The characteristics of Element SampleNo. 20 as a solar cell are evaluated in the same manner as in Example 1.

The results obtained are shown in Table 27.

Besides the foregoing, using a quartz glass plate, there was formed ann-type poly-BP:H:F:Se semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the n-typesemiconductor layer 103.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 27.

EXAMPLE 21

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(B)(Element Sample No. 21) basically inaccordance with the manner of Example 1 and the manner of Example 8.

That is, as the substrate 101, there was used a Corning glass plate No.7059 of 50 mm by 50 mm in size. On the substrate an ITO thin film ofabout 500 Å in thickness as the transparent electrode 106 was formed bythe resistance heating method. On the transparent electrode was formed a200 Å thick p-type ZnTe:P semiconductor film as the p-type semiconductorlayer 105 by the foregoing process (2) by the reactive sputtering methodpracticed in the reactive sputtering apparatus shown in FIG. 3 under theconditions shown in Table 28. Then, the procedures for forming thei-type semiconductor layer in Example 1 were repeated to form a 3500 Åthick non-doped i-type a-Si:H:F film as the i-type semiconductor layer104 on the p-type semiconductor layer.

Successively, there was formed a 400 Å thick n-type poly-BP:H:F:Sesemiconductor film as the n-type semiconductor layer 103 on the i-typesemiconductor layer 104 by repeating the procedures of forming then-type semiconductor layer in Example 8. On this n-type semiconductorwas formed a 0.5 um thick Ag film as the electrode 102. Thus there wasobtained Element Sample No. 21. The characteristics of Element SampleNo. 21 as a solar cell were evaluated in the same manner as in Example1.

The results obtained are shown in Table 27.

Besides the foregoing, using a quartz glass plate, there was formed ann-type poly-BP:H:F:Se semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the n-typesemiconductor layer 103.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 27.

EXAMPLE 22

There was prepared a pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(B)(Element Sample No. 22) basically inaccordance with the manner of Example 1 and the manner of Example 8.

That is, as the substrate 101, there was used a Corning glass plate No.7059 of 50 mm by 50 mm in size. On the substrate was formed an ITO thinfilm of about 500 Å in thickness as the transparent electrode 106 by theresistance heating method.

On the transparent electrode was formed a 200 Å thick p-type BP:Znsemiconductor film as the p-type semiconductor layer by the foregoingprocess (2) by the reacting sputtering method practiced in the reactivesputtering apparatus shown in FIG. 3 under the conditions shown in 29.Then, the procedures for forming the i-type semiconductor layer inExample 1 were repeated to form a 3500 Å thick non-doped i-type a-Si:H:Ffilm as the i-type semiconductor layer 104 on the p-type semiconductorlayer. Successively, there was formed a 400 Å thick n-typepoly-BP:H:F:Se semiconductor film as the n-type semiconductor layer 103on the i-type semiconductor layer 104 by repeating the procedures offorming the n-type semiconductor layer in Example 8. On this n-typesemiconductor was formed a 0.5 μm thick Ag film as the electrode 102.Thus there was obtained Element Sample No. 22. The characteristics ofElement Sample No. 22 as a solar cell were evaluated in the same manneras in Example 1.

The results obtained are shown in Table 27.

Besides the foregoing, using a quartz glass plate, there was formed ann-type poly-BP:H:F:Se semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the n-typesemiconductor layer 103.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 27.

EXAMPLE 23

There was prepared a multi-cell tandem stacked pin heterojunctionphotovoltaic element of the configuration shown in FIG. 1(C)(ElementSample 23) which comprises three cell stacked in the following manner.

As the substrate 101, there was used a stainless plate of 50 mm by 50 mmin size.

Firstly, on the substrate was formed a 1000 Å thick Ag thin film as thelower electrode 102 in the same manner as in Example 1.

On the lower electrode was then formed a pin heterojunction photovoltaicelement as the first cell 111 comprising a 400 Å thick n-type a-Si:H:F:Psemiconductor film as the n-type semiconductor layer, a 3500 Å thicknon-doped i-type a-SiGe:H:F semiconductor film as the i-typesemiconductor layer 104 and a 200 Å thick p-type poly-BP:H:F:Znsemiconductor film as the p-type semiconductor layer 105 by repeatingthe procedures of Example 5. Then, a second pin heterojunctionphotovoltaic element as the second cell 112 comprising a 400 Å thickn-type a-Si:H:F:P semiconductor film as the n-type semiconductor layer114, a 3000 Å thick i-type non-doped a-Si:H:F film as the i-typesemiconductor layer 115 and a 200 Å thick p-type poly-BP:H:F:Znsemiconductor film as the p-type semiconductor layer 116 was formed onthe first cell 111 by repeating the procedures of Example 1. On thesecond cell 112 there was formed a pin heterojunction photovoltaicelement as the third cell 113 comprising a 400 Å thick n-type a-Si:H:F:Psemiconductor film as the n-type semiconductor layer 117, a 2500 Å thicknon-doped i-type a-SiC:H:F semiconductor film as the i-typesemiconductor layer 118 and a 200 Å thick p-type poly-BP:H:F:Znsemiconductor film as the p-type semiconductor layer 119 by repeatingthe procedures of Example 4. On the p-type semiconductor layer 119 ofthe third cell 113 there was formed a 700 Å ITO film as the transparentelectrode 106 in the same manner in Example 1. On the transparentelectrode, there was formed a comb-shaped film comprising an Ag thinfilm of 0.8 μm in thickness as the collecting electrode 107 by repeatingthe procedures of forming the comb-shaped collecting electrode inExample 1. Thus there was obtained Element Sample No. 23. Thecharacteristics of Element Sample No. 23 as a solar cell were evaluatedin the same manner as in Example 1.

The results obtained are shown in Table 30.

COMPARATIVE EXAMPLE 1

There was prepared a comparative pin heterojunction photovoltaic elementof the configuration shown in FIG. 1(A)(Element Sample No. 24) byrepeating the procedures of Example 1, except that the p-typesemiconductor layer 105 was formed of a 200 Å thick p-type a-Si:H:F:Bsemiconductor film which was prepared in the following manner.

That is, after the i-type semiconductor layer 104 was formed, thesubstrate was moved by the substrate transfer unit through the gatevalve to the other film-forming chamber having the same constitution asthat of the film-forming chamber 201. The gate valve was closed and thefilm-forming chamber was evacuated to and maintained at 1×10⁻⁵ Torr orbelow. The substrate was then heated to 220° C. by actuating the heater205 and it was maintained at this temperature. Thereafter, Si₂ F₆ gasand BF₃ gas diluted with SiF₄ gas to 4000 ppm (BF₃ /SiF₄ gas) wereintroduced through the gas supply pipe 214 into the activation chamber208 maintained at 700° C. by the activation energy generation means 211at respective flow rates of 30 sccm and 8 sccm while being mixed togenerate precursors containing fluorine radicals, which weresuccessively introduced through the transport conduit 217 into thefilm-forming chamber 201.

At the same time, He gas and H₂ gas were introduced through the gassupply pipe 215 into the activation chamber 209 at respective flow ratesof 120 sccm and 60 sccm while being mixed, into which microwave power(2.45 GHz) of 320 W was applied to generate hydrogen radicals, whichwere successively introduced through the transport conduit 218 into thefilm-forming chamber 201. At this time, the inner pressure of thefilm-forming chamber 201 was maintained at 0.35 Torr. The foregoingprecursors and hydrogen radicals thus introduced into the film-formingchamber 201 were chemically reacted to form a 200 Å thick p-typea-Si:H:F:B semiconductor film as the p-type semiconductor layer 105 onthe i-type semiconductor layer 104. On this p-type semiconductor weresuccessively formed a 700 Å thick ITO film as the transparent electrode106 and a 0.8 μm thick comb-shaped film comprising a 0.8 μm thick Agfilm as the collecting electrode 107 respectively in the same manner asin Example 1.

Thus there was obtained Element Example No. 24 for comparison purposes.

The characteristics of Element Sample No. 24 as a solar cell wereevaluated in the same manner as in Example 1.

The results obtained are shown in Table 31.

COMPARATIVE EXAMPLE 2

There was prepared a comparative pin heterojunction photovoltaic elementof the configuration shown in FIG. 1(A)(Element Sample No. 25) byrepeating the procedures of Example 1, except that the p-typesemiconductor layer 105 was formed of a 200 Å thick p-type poly-BP:F:Znsemiconductor film which was prepared by repeating the procedures offorming the p-type semiconductor layer in Example 1, except that H₂ gaswas not used.

Likewise, there was separately prepared another comparative pinheterojunction photovoltaic element of the configuration shown in FIG.1(A)(Element Sample No. 26) by repeating the procedures of Example 1,except that the p-type semiconductor layer 105 was formed of a 200 Åthick p-type poly-BP:H:F:Zn semiconductor film (wherein the hydrogencontent is slight) which was prepared by repeating the procedures ofExample 1, except for changing the flow rate of the H₂ gas to 0.5 sccm.

The characteristics of each of Element Samples Nos. 25 and 26 as a solarcell were evaluated in the same manner as in Example 1.

The results obtained are shown in Table 31.

Besides the foregoing, using a quartz glass plate, there was formed eachof the foregoing two p-type semiconductor films on the quartz glassplate by repeating the respective foregoing procedures for the formationof the p-type semiconductor layer 105.

Each of the resultant films was examined for hydrogen content, fluorinecontent, and the average size of crystal grains in the film in the samemanner as above described.

The results are shown in Table 31.

COMPARATIVE EXAMPLE 3

There was prepared a comparative pin heterojunction photovoltaic elementof the configuration shown in FIG. (A)(Element Sample No. 27) byrepeating the procedures of Example 1, except that the flow rate of theraw material gas containing B₂ H₆ /Zn(CH₃)₂ =10⁻⁴ :1 and the flow rateof the PF₅ gas at the time of forming the p-type semiconductor layerwere changed respectively to 5.0×10⁻⁴ mol/min and 15 sccm.

The characteristics of Element Sample No. 27 as a solar cell wereevaluated in the same manner as in Example 1.

The results obtained are shown in Table 31.

Besides the foregoing, using a quartz glass plate, there was formed theforegoing p-type semiconductor film on the quartz glass plate byrepeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

The resultant film was examined for hydrogen content, fluorine content,and the average size of crystal grains in the film in the same manner asabove described.

The results are shown in Table 31.

COMPARATIVE EXAMPLE 4

There were prepared three kinds of comparative pin heterojunctionphotovoltaic elements of the configuration shown in FIG. 1(A)(ElementSamples Nos. 28, 29 and 30) by repeating the procedures of Example 1,except that the i-type semiconductor layer 104 was formed of a 3500 Åthick non-doped i-type a-Si film, a-SiC film or a-SiGe film prepared bythe foregoing process (2) by the reactive sputtering apparatus shown inFIG. 2 under the conditions shown in Table 32.

The characteristics of each of Element Samples Nos. 28, 29 and 30 as asolar cell were evaluated in the same manner as in Example 1.

The results obtained are shown in Table 31.

Besides the foregoing, using a quartz glass plate, each of the p-typepoly-AlP:H:F:Zn semiconductor films was formed on the quartz glass plateby repeating the foregoing procedures for the formation of the p-typesemiconductor layer 105.

Each of the resultant films was examined for hydrogen content, fluorinecontent, and the average size of crystal grains in the film in the samemanner as above described.

The results are shown in Table 31.

COMPARATIVE EXAMPLE 5

There was prepared a comparative multi-cell tandem stacked pinheterojunction photovoltaic element of the configuration shown in FIG.1(C)(Element Sample 31) by repeating the procedures of Example 23,except that the p-type semiconductor layer 119 of the third cell 113 wasformed of a 200 Å thick p-type a-Si:H:F:B film by repeating theprocedures of forming the p-type semiconductor layer in ComparativeExample 1.

The characteristics of Element Sample 31 were evaluated in the samemanner as in Example 1. The results obtained are shown in Table 30.

Observations on the Results Shown in Tables 9, 17, 27, 30 and 31

In each of Tables 9, 17, 27, 30 and 31, with respect to characteristicproperties required for a pin heterojunction photovoltaic element, thereare indicated the following evaluation items: (a) open-circuit voltage(Voc) which is generated when the element is irradiated with AM-1 light(100 mW/cm²), (b) short-circuit current (Isc) which is generated whenthe element is irradiated with AM-1 light (100 mW/cm²), and (c) therelative value of the output which is obtained when the element isirradiated with AM-1 light through a 400 nm interference filter versusthe output which is obtained when the pin heterojunction photovoltaicelement prepared in Comparative Example 1 is irradiated through theinterference filter.

In each of Tables 9, 17, 27 and 31, there are also shown the content ofhydrogen atoms (H), the content of optional fluorine atoms (F), theaverage grain size, and the composition ratio of the B to the P withrespect to each of the poly-BP:H(F):M semiconductor films used.

The results indicate the following. It has been recognized that each ofthe pin heterojunction photovoltaic elements of the configuration shownin FIG. 1(A) or FIG. 1(B) (Element Samples Nos. 1-22 obtained inExamples 1 to 22) having the p-type semiconductor layer or/and then-type semiconductor layer formed of a specific polyBP:H(F):Msemiconductor film of wide band gap (where M is a dopant of p-type orn-type) according to the present invention which contains boron atoms(B) and phosphorous atoms (P) in uniformly distributed states with thecomposition ratio of the Al to the P to satisfy the stoichiometricratio, hydrogen atoms (H) in an amount of 0.5 to 7 atomic optionallyfluorine atoms (F) in an amount of 0 to 3 atomic %, and crystal grainsof an average size in the range of from 50 to 800 Å and the i-typesemiconductor layer of a specific silicon (Si)-containing non-singlecrystal film containing at least hydrogen atoms (H) and/or fluorineatoms (F) excels in any of the evaluation items required for a solarcell. It has been also recognized that the specific poly-BP:H(F):Msemiconductor film according to the present invention makes it possibleto form a desirable junction with a specific silicon(Si)-containingnon-single crystal semiconductor film regardless of its band gap whetherit is wide or narrow and thus, it makes possible to provide a desirablepin heterojunction photovoltaic element excelling in the characteristicsrequired for a solar cell. This situation is apparent when thecharacteristics of each of these pin heterojunction photovoltaicelements (Element Samples Nos. 1 to 22) as a solar cell are comparedwith those of each of the comparative pin junction photovoltaic elementsof the configuration shown in FIG. 1(A) (Element Samples Nos. 24 to 30prepared in Comparative Examples 1 to 4). More particularly in thisrespect, it has been recognized that the pin heterojunction photovoltaicelements (Element Samples 1 to 3 prepared in Examples 1 to 3 ,respectively) in which the p-type semiconductor layer comprises theforegoing specific poly-BP:H(F):Mp semiconductor film (where Mp is ap-type dopant) prepared by a different film-forming method, the i-typesemiconductor layer comprising the foregoing selected Si-containingnon-single crystal film (a-Si:H:F film) and the n-type semiconductorlayer comprising an n-type non-single crystal Si-containing film (n-typea-Si:H:F film) markedly surpass the comparative pin photovoltaic element(Element Sample No. 24 prepared in Comparative Example 1) which has thep-type semiconductor layer comprising a p-type a-Si:H:F film, the i-typesemiconductor layer comprising an i-type aSi:H:F film and the n-typesemiconductor layer comprising an n-type a-Si:H:F film, with respect toeach of the foregoing evaluation items (a) to (c) without depending uponthe kind of the method employed for forming said poly-BP:H(F):Mpsemiconductor film.

For the pin heterojunction photovoltaic elements (Element Samples Nos.4, 5 and 6 prepared respectively in Examples 4, 5 and 6) respectivelycomprising a p-type semiconductor layer formed of the foregoingpoly-BP:H(F):Mp semiconductor film, an i-type semiconductor layer formedof an i-type a-SiC:H:F film, an i-type a-SiGe:H:F film or an i-typepoly-Si:H:F film and an n-type semiconductor layer formed of an n-typea-Si:H:F film, it has been recognized that each of them still excels ineach of the evaluation items (a) to (c) although the i-typesemiconductor layer is formed of a Si-containing non-single crystal filmother than an i-type a-Si:H:F film, i.e. said i-type a-SiC:H:F film, itype a-SiGe:H:F film or i-type poly-Si:H:F film.

From the results of the pin heterojunction photovoltaic element (ElementSample No. 7 prepared in Example 7), it has been recognized that thepresent invention is markedly effective also in the case of pinheterojunction photovoltaic elements of the type wherein light isimpinged from the side of the substrate. In fact, as Table 9illustrates, the pin heterojunction photovoltaic element of theconfiguration shown in FIG. 1(B) which comprises the p-typesemiconductor layer formed of p-type a-Si:H:F, the i-type semiconductorlayer formed of i-type a-Si:H:F film and the n-type semiconductor layerformed of the foregoing poly-BP:H(F):Mn film (where Mn is an n-typedopant) markedly excels in each of the foregoing evaluation items (a) to(c).

From the results shown in Table 9 for the pin heterojunctionphotovoltaic element (Element Sample No. 8 prepared in Example 8) whichcomprises a p-type semiconductor layer formed of the foregoingpoly-BP:H(F):Mp semiconductor film, an i-type semiconductor layer formedof an i-type a-Si:H:F film and an n-type semiconductor layer formed ofthe foregoing poly-BP:H(F):Mn semiconductor film, it has been recognizedthat Element Sample No. 8 surpasses each of Element Samples 1 to 3 withrespect to all the foregoing evaluation items (a) to (c).

On the other hand, for the two comparative pin heterojunctionphotovoltaic elements (Element Samples Nos. 25-26 prepared inComparative Example 2), it has been recognized that each of themapparently is inferior to each of Element Samples Nos. 1-3 chieflybecause each of them has the p-type semiconductor layer formed of ap-type poly-BP:F semiconductor film not containing hydrogen atoms or ap-type poly-BP:H:F semiconductor film containing hydrogen atoms only ina slight amount.

Likewise, for the comparative pin heterojunction photovoltaic element(Element Sample No. 27 prepared in Comparative Example 3), it has beenrecognized that it is apparently inferior to each of Element SamplesNos. 1 to 3 chiefly because of having a p-type semiconductor layerformed of a p-type poly-BP:H:F film containing boron atoms (B) andphosphorus atoms (P) with a composition ratio which does not satisfy thestoichiometric ratio.

For the three comparative pin heterojunction photovoltaic elements(Element Samples Nos. 28-30), it has been recognized that each of themis apparently inferior to each of Element Samples Nos. 3-5 although eachof them has a p-type semiconductor layer formed of the foregoingpoly-BP:H:F:Mp semiconductor film but it has the i-type semiconductorlayer formed of an i-type a-Si film, a-SiC film or a-SiGe filmcontaining neither hydrogen atoms (H) nor fluorine atoms (F).

For the pin heterojunction photovoltaic elements (Element Samples Nos.9-12 prepared in Examples 9-12) respectively having a p-typesemiconductor layer formed of the foregoing poly-BP:H(F):Mpsemiconductor film, an i-type semiconductor layer formed of an i-typea-Si:H:F film and an n-type semiconductor layer formed of an n-typenon-single crystal film other than an n-type a-Si:H:F film, i.e. ann-type BP film, an n-type a-SiGe:H:F film of narrow band gap, an n-typea-SiC:H:F film of wide band gap or an n-type GaAs film of narrow bandgap, it has been recognized that each of them provides a high Voc and adesirable Isc, and exhibits good, practically applicable solar cellcharacteristics.

For the pin heterojunction photovoltaic elements (Element Samples Nos.13-18 prepared in Examples 13-18) respectively having a p-typesemiconductor layer formed of the foregoing poly-BP:H(F):Mpsemiconductor film, an i-type semiconductor layer formed of an i-typeSi-containing non-single crystal film other than the i-type a-Si:H:Ffilm i.e. an i-type a-Si:H film, an i-type a-SiGe:H film of narrow bandgap, an i-type a-SiC:H film of wide band gap, an i-type a-Si:F film, ani-type a-Si:Ge:C:H film of wide band gap or an i-type poly-Si:H film ofnarrow band gap, and an n-type semiconductor layer formed of theforegoing poly-BP:H(F): Mn semiconductor film, it has been recognizedthat each of them provides a high Voc and a desirable Isc, and exhibitspractically applicable good solar cell characteristics.

For the pin heterojunction photovoltaic elements (Element Samples Nos.19-22 prepared in Examples 19-22) of the configuration shown in FIG.1(B) respectively having a p-type semiconductor layer formed of a p-typea-Si:H:F film, a p-type a-SiC:H:F film of wide band gap, a p-type ZnTefilm of wide band gap or a p-type BP film of wide band gap, an i-typesemiconductor layer formed of an i-type a-Si:H:F film and an n-typesemiconductor layer formed of the foregoing poly-BP:H(F):Mnsemiconductor film, it has been recognized that each of them provides ahigh Voc and a desirable Isc, and exhibits good practically applicablesolar cell characteristics.

For each of the multi-cell tandem stacked pin heterojunctionphotovoltaic elements of the configuration shown in FIG. 1(c)(ElementSamples Nos. 23 and 31 prepared in Examples 21 and Comparative Example5), evaluations were made of the Voc and the Isc and in addition, forthe change in photoelectric conversion efficiency that takes place aftercontinuous irradiation with AM-1 light for 10 hours: the change isexpressed by Δ.sub.η η_(o) in percentage, where Δ.sub.η is the amount ofchange in photoelectric conversion efficiency and η_(o) is the initialphotoelectric conversion efficiency as shown in Table 30.

From the results shown in Table 30, it has been recognized that (1) themulti-cell tandem stacked pin heterojunction photovoltaic element inwhich the p-type semiconductor layer of each cell is formed of theforegoing poly-BP:H(F):Mp semiconductor film (Element Sample No. 23) issuperior to the comparative multi-cell tandem stacked pin heterojunctionphotovoltaic element (Element Sample No. 31) in which the p-typesemiconductor layer of each cell is formed of a p-type a-Si:H:F filmwith respect to Voc and the Isc. It has been also recognized that thechange in photoelectric conversion efficiency of Element Sample No. 23is significantly smaller than that of Element Sample No. 31. This meansthat Element Sample No. 23 not only excels in the initial solar cellcharacteristics but also can be continuously used as a solar cell for along period of time without being deteriorated.

                                      TABLE 1    __________________________________________________________________________    substrate temperature: 220° C.    inner pressure: 80 mTorr    raw material gas (A):                  B(CH.sub.3).sub.3 gas at 5 sccm                              decomposed with    (introduced into                  He gas(carrier gas)                              microwave(2.45 GHz)    the activation                  at 20 sccm  of 80 W    chamber 208)    raw material gas (B):                  PF.sub.5 gas at 5 sccm                              thermally decomposed    (introduced into          at 500° C.    the activation    chamber 210)    raw material gas (C):                  H.sub.2 gas* at 0˜1000 sccm,                              decomposed with    (introduced into                  He gas at 50 sccm                              microwave(2.45 GHz)    the activation            of 200 W    chamber 209)    the distance between the substrate and the outlet    of the transportation conduit for H radicals: 10 cm    *Sample No. and the flow rate of H.sub.2 gas    Sample No. 1           0 sccm    Sample No. 2           0.2 sccm    Sample No. 3           1.0 sccm    Sample No. 4           5.0 sccm    Sample No. 5           10 sccm    Sample No. 6           15 sccm    Sample No. 7           30 sccm    Sample No. 8           80 sccm    Sample No. 9           500 sccm     Sample No. 10         1000 sccm    __________________________________________________________________________

                                      TABLE 2    __________________________________________________________________________    Sample        hydrogen content                 fluorine content                         composition ratio of                                   distributed state                                            crystal                                                  average crystal    No. (atomic %)                 (atomic %)                         B to P    of crystal grain                                            orientation                                                  grain size    __________________________________________________________________________                                                  (Å)    1   not detected                 7.4     40:66     uneven(localized)                                            random                                                  --    2   0.3      5.1     43:57     "        "     --    3   2.6      3.2     48:52     even     <111>  50    4   3.3      3.0     50:50     "        "     200    5   4.3      2.5     50:50     "        "     600    6   4.6      1.2     51:49     "        "     650    7   4.9      0.9     52:48     "        "     750    8   4.5      0.8     52:48     "        "     800    9   3.2      0.3     53:47     "        "     700    10  2.4       0.05   56:44     "        "     600    __________________________________________________________________________

                  TABLE 3    ______________________________________    target material: non-doped polycrystal BP wafer    sputtering gas used:                      Ar gas at 30 sccm    and its flow rate H.sub.2 gas* at 0˜300 sccm                      HF gas* at 0˜80 sccm    the distance between the target and the substrate: 30 mm    high frequency power: 500 W (13.56 MHz)    substrate temperature: 200° C.    inner pressure: 4.5 mTorr    *Sample No. and the flow rates of H.sub.2 gas and HF gas                    H.sub.2   HF    Sample No. 11    0 sccm   0 sccm    Sample No. 12    1 sccm   1 sccm    Sample No. 13    3 sccm   0 sccm    Sample No. 14    8 sccm   8 sccm    Sample No. 15   10 sccm   8 sccm    Sample No. 16   25 sccm   8 sccm    Sample No. 17   50 sccm   50 sccm    Sample No. 18   80 sccm   50 sccm    Sample No. 19   80 sccm   80 sccm    Sample No. 20   300 sccm  80 sccm    ______________________________________

                                      TABLE 4    __________________________________________________________________________    Sample        hydrogen content                 fluorine content                         composition ratio of                                   distributed state                                            crystal                                                  average crystal    No. (atomic %)                 (atomic %)                         B to P    of crystal grain                                            orientation                                                  grain size    __________________________________________________________________________                                                  (Å)    11  not detected                 not detected                         44:56     fairly uneven                                            random                                                  --    12  0.1      not detected                         46:54     even     <111>  20    13  0.5       0.05   47:53     "        "      50    14  0.8      0.1     48:52     "        "     200    15  2.0      0.3     49:51     "        "     250    16  4.8      1.6     50:50     "        "     550    17  6.1      2.5     51:49     "        "     750    18  7.0      2.8     51:49     "        "     800    19  7.2      4.3     53:47     "        "     700    20  8.0      2.0     50:50     "        "     600    __________________________________________________________________________

                  TABLE 5    ______________________________________    raw material gas (A):                      gasified B(CH.sub.3).sub.3 at 3 sccm                      He gas at 10 sccm    raw material gas (B):                      PH.sub.3 gas at 3 sccm    raw material gas (C):                      H.sub.2 gas* at 0˜800 sccm                      HF gas* at 0˜80 sccm    the distance between the substrate and the cathode: 30 mm    high frequency power: 80 W (13.56 MHz)    substrate temperature: 230° C.    inner pressure: 0.8 Torr    *Sample No. and the flow rates of H.sub.2 gas and HF gas                    H.sub.2   HF    Sample No. 21    0 sccm    0 sccm    Sample No. 22    8 sccm    0 sccm    Sample No. 23    10 sccm  10 sccm    Sample No. 24   100 sccm  50 sccm    Sample No. 25   100 sccm  80 sccm    Sample No. 26   200 sccm  100 sccm    Sample No. 27   300 sccm  30 sccm    Sample No. 28   500 sccm  30 sccm    Sample No. 29   800 sccm  50 sccm    Sample No. 30   800 sccm  80 sccm    ______________________________________

                                      TABLE 6    __________________________________________________________________________    Sample        hydrogen content                 fluorine content                         composition ratio of                                   distributed state                                            crystal                                                  average crystal    No. (atomic %)                 (atomic %)                         B to P (atomic %)                                   of crystal grain                                            orientation                                                  grain size    __________________________________________________________________________                                                  (Å)    21   20      not detected                         45:55     uneven(localized)                                            amorphous                                                  --    22   16      not detected                         46:54     "        "     --    23   10      0.3     48:52     fairly uneven                                            "     --    24  7.0      1.5     48:52     even     random                                                   20    25  5.6      1.2     49:51     "        <111> 100    26  5.8      2.3     51:49     "        "     350    27  3.5      1.1     51:49     "        "     450    28  1.8      1.3     50:50     "        "     750    29  1.6      1.2     50:50     "        "     650    30  2.3      2.3     52:48     "        "     600    __________________________________________________________________________

                                      TABLE 7    __________________________________________________________________________    Sample         change in the electric                    photo-  surface                                  total    No.  conductivity                    luminescence                            smoothness                                  evaluation    __________________________________________________________________________     1   X          X       X     X     2   X          X       X     X     3   ○   X       X     X     4   ○   Δ ○                                  ○     5   ○   ○                            ○                                  ⊚     6   ○   ○                            ○                                  ⊚     7   ○   ○                            ○                                  ⊚     8   ○   ○                            ○                                  ⊚     9   ○   ○                            X     X    10   ○   ○                            X     X    11   X          X       X     X    12   X          X       X     X    13   ○   Δ ○                                  ○    14   ○   ○                            ○                                  ⊚    15   ○   ○                            ○                                  ⊚    16   ○   ○                            ○                                  ⊚    17   ○   Δ ○                                  ○    18   ○   Δ ○                                  ○    19   X          X       X     X    20   X          Δ X     X    21   X          X       X     X    22   X          X       X     X    23   X          X       X     X    24   X          Δ X     X    25   ○   ○                            ○                                  ⊚    26   ○   Δ ○                                  ○    27   ○   ○                            ○                                  ⊚    28   ○   ○                            ○                                  ⊚    29   ○   ○                            X     X    30   ○   Δ X     Δ    __________________________________________________________________________     Note     ⊚: excellent     ○  : good     Δ: seems practically acceptable     X: practically not acceptable

                                      TABLE 8    __________________________________________________________________________    Sample        p-type    i-type  n-type    No. semiconductor                  semiconductor                          semiconductor                                   I sc                                      V oc    __________________________________________________________________________     91 p-type BP:H(F)                  A-Si:H  A-Si:H   ○                                      ○     92 according to the                  A-Si:F           Δ                                      ○     93 present   A-Si:H:F         ○                                      ○     94 invention A-Si:H  n-type BP:H(F)                                   ○⊚     95           A-Si:F  according to the                                   ○                                      ○     96           A-Si:H:F                          present  ○                                      ⊚                          invention     97           A-SiC:H:F                          A-Si:H   Δ                                      ⊚     98           A-SiGe:H:F       ⊚                                      Δ     99           poly-Si:H:F      ○                                      Δ    100           A-Si    A-Si:H   X  X    101           A-SiC            X  Δ    102           A-SiGe           X  X    103           poly-Si          Δ                                      X    104 known p-type BP                  A-Si:H  A-Si:H   X  Δ    105           A-Si:F           X  X    106           A-Si:H:F         X  X    107           A-SiC:H:F        X  Δ    108           A-SiGe:H:F       X  X    109           poly-Si:H:F      X  Δ    __________________________________________________________________________     ⊚: excellent     ○  : good     Δ: seems practically acceptable     X: practically not acceptable

                                      TABLE 9    __________________________________________________________________________                         characteristics of p-type & n-type BP:H(F)film                                            average                                            crystal                                                 composition    Example         Element               semiconductor                         hydrogen content                                  fluorine  grain size                                                 ratio of B    No.  Sample No.               layer     (atomic %)                                  content(atomic %)                                            (Å)                                                 to P    __________________________________________________________________________    1    1     p-type BP:H:F(1)                         4.1      1.0       500  50:50               i-type A-Si:H:F               n-type A-Si:H:F    2    2     p-type BP:H:F(2)                         3.0      1.5       600  51:49               i-type A-Si:H:F               n-type A-Si:H:F    3    3     p-type BP:H:F(3)                         4.5      1.2       400  51:49               i-type A-Si:H:F               n-type A-Si:H:F    4    4     p-type BP:H:F                         4.0      1.1       500  51:49               i-type A-SiC:H:F               n-type A-Si:H:F    5    5     p-type BP:H:F                         4.2      1.0       500  50:50               i-type A-SiGe:H:F               n-type A-Si:H:F    6    6     p-type BP:H:F                         4.1      1.2       500  51:49               i-type polySi:H:F               n-type A-Si:H:F    7    7     p-type A-Si:H:F                         4.0      1.1       450  50:50               i-type A-Si:H:F               n-type BP:H:F    8    8     p-type BP:H:F                         4.1      1.0       500  51:49               i-type A-Si:H:F                         *4.0     0.9       450  50:50               n-type BP:H:F    __________________________________________________________________________                               open-circuit                                      short-circuit                                             output value under                               voltage under                                      photocurrent                                             irradiation of                               irradiation of                                      under irradia-                                             AM-1 light(using                               AM-1 light                                      tion of AM-1                                             400 nm interference                          Example                               Voc    light  filter)                          No.  [Volt] Isc [mA/cm.sup.2 ]                                             [relative value]    __________________________________________________________________________                          1    0.98   17.4   1.8                          2    0.97   17.3   1.7                          3    0.97   16.8   1.8                          4    1.16   12.1   1.5                          5    0.72   20.7   1.5                          6    0.69   18.2   1.2                          7    0.95   17.2   1.7                          8    0.96   18.3   2.0    __________________________________________________________________________     *n-type BP:H(F)film

                  TABLE 10    ______________________________________    target material: non-doped BP polycrystal wafer    substrate temperature: 220° C.    flow rate of Ar gas: 50 sccm    flow rate of H.sub.2 gas: 20 sccm    flow rate of HF gas: 10 sccm    flow rate of DMZn gas                       2 × 10.sup.-10 mol/min    as a carrier gas:    inner pressure: 6.5 mTorr    high frequency power: 400 W (13.56 MHz)    ______________________________________

                  TABLE 11    ______________________________________    substrate temperature: 230° C.    raw material gas (A):                    gasified B(CH.sub.3).sub.3 /Zn(CH.sub.3).sub.2 =                    10.sup.4 :1 at 5.0 × 10.sup.-4 mol/min                    He gas at 30 sccm    raw material gas (B):                    PH.sub.3 gas at 3.0 sccm    raw material gas (C):                    H.sub.2 gas at 100 sccm                    HF gas at 100 sccm    inner pressure: 0.7 Torr    high frequency power: 100 W (13.56 MHz)    the distance between the substrate and the cathode: 30 mm    ______________________________________

                  TABLE 12    ______________________________________    raw material gas (A):                 Si.sub.2 F.sub.6 gas at                              thermally decomposed    (introduced into                 30 sccm      at 700° C.    the activation    chamber 208)    raw material gas (B):                 H.sub.2 gas at                              decomposed with    (introduced into                 150 sccm     microwave (2.45GHz)    the activation                 He gas at    of 400W    chamber 209) 100 sccm    raw material gas (C):                 CH.sub.4 gas at                              decomposed with    (introduced into                 150 sccm     microwave (2.45GHz)    the activation                 He gas at 20 sccm                              of 300W    chamber 210)    substrate temperature: 220° C.    inner pressure: 0.20 Torr    the distance between the substrate and the outlet    of the transportation conduit for H radicals: 5 cm    ______________________________________

                  TABLE 13    ______________________________________    raw material gas (A):                 Si.sub.2 F.sub.6 gas at                              thermally decomposed    (introduced into                 30 sccm      at 700° C.    the activation    chamber 208)    raw material gas (B):                 H.sub.2 gas at 80 sccm                              decomposed with    (introduced into                 He gas at 50 sccm                              microwave (2.45GHz)    the activation            of 400W    chamber 209)    raw material gas (C):                 GeF.sub.4 gas at                              thermally decomposed    (introduced into                 4 sccm       at 450° C. together    the activation                 He gas at 30 sccm                              with Ge solid    chamber 210)              particles    substrate temperature: 220° C.    inner pressure: 0.10 Torr    the distance between the substrate and the outlet    of the transportation conduit for H radicals: 8 cm    ______________________________________

                  TABLE 14    ______________________________________    raw material gas (A):                 Si.sub.2 F.sub.6 gas at                              thermally decomposed    (introduced into                 20 sccm      at 700° C.    the activation    chamber 208)    raw material gas (B):                 H.sub.2 gas at                              decomposed with    (introduced into                 300 sccm     microwave (2.45GHz)    the activation                 He gas at    of 450W    chamber 209) 100 sccm    substrate temperature: 220° C.    inner pressure: 0.26 Torr    the distance between the substrate and the outlet    of the transportation conduit for H radicals: 8 cm    ______________________________________

                  TABLE 15    ______________________________________    raw material gas (A):                 gasified B(CH.sub.3).sub.3 /                              decomposed with high    (introduced into                 Se(CH.sub.3).sub.2 =10.sup.4 :1                              frequency power    the activation                 at 4.0 × 10.sup.-4                              (13.56 MHz) of 80W    chamber 208) mol/min                 He gas at 10 sccm    raw material gas (B):                 H.sub.2 gas at 6 sccm                              decomposed with    (introduced into                 He gas at 60 sccm                              microwave (2.45 GHz)    the activation            of 50 W    chamber 209)    raw material gas (C):                 PF.sub.5 gas at 5 sccm                              thermally decomposed    (introduced into          at 500° C.    the activation    chamber 210)    substrate temperature: 220° C.    inner pressure: 0.8 Torr    the distance between the substrate and the outlet    of the transportation conduit for H radicals: 8 cm    ______________________________________

                  TABLE 16    ______________________________________    target material: non-doped BP polycrystal wafer    substrate temperature: 220° C.    flow rate of Ar gas: 30 sccm    flow rate of Se(CH.sub.3).sub.2 saturated with He gas    (as an n-type doping raw material gas): 3 × 10.sup.-11 mol/min    flow rate of He gas: 2 sccm    inner pressure: 5 mTorr    high frequency power: 350W (13.56MHz)    ______________________________________

                                      TABLE 17    __________________________________________________________________________                        characteristics of p-type &                        n-type BP:H(F)film   open-cir-                                                   short-circuit                                                          output value                                    average  cuit voltage                                                   photocurrent                                                          under irradiation                                    crystal                                         compo-                                             under ir-                                                   under irradia-                                                          of AM-1 light         Element        hydrogen                              fluorine                                    grain                                         sition                                             radiation of                                                   tion of AM-1                                                          (using 400 nm in-    Example         Sample              semiconductor                        content                              content                                    size ratio of                                             AM-1 light                                                   light  terference filter)    No.  No.  layer     (atomic %)                              (atomic %)                                    (Å)                                         B to P                                             Voc [Volt]                                                   Isc [mA/cm.sup.2 ]                                                          [relative    __________________________________________________________________________                                                          value]     9    9   p-type BP:H:F                        4.1   1.0    500  50:50                                             0.95  17.2   1.6              i-type A-Si:H:F              n-type BP    10   10   p-type BP:H:F                        4.0   1.1   500  50:50                                             0.92  17.0   1.5              i-type A-Si:H:F              n-type A-SiGe:H:F    11   11   p-type BP:H:F                        3.9   1.1   500  51:49                                             0.97  18.1   1.9              i-type A-Si:H:F              n-type A-SiC:H:F    12   12   p-type BP:H:F                        4.1   1.1   500  51:49                                             0.95  17.0   1.4              i-type A-Si:H:F              n-type GaAs    13   13   p-type BP:H:F                        *4.0  1.0   500  50:50                                             0.97  17.2   1.9              i-type A-Si:H              n-type BP:H:F                        **3.9 0.9   450  50:50    14   14   p-type BP:H:F                        *4.1  1.0   500  50:50                                             0.60  20.2   1.2              i-type A-SiGe:H              n-type BP:H:F                        **4.2 0.9   450  51:49    15   15   p-type BP:H:F                        *4.1  1.1   500  51:49                                             1.25  12.0   1.3              i-type A-SiC:H              n-type BP:H:F                        **4.0 1.0   450  50:50    16   16   p-type BP:H:F                        *4.0  1.1   500  51:49                                             0.91  17.2   1.4              i-type A-Si:F              n-type BP:H:F                        **4.0 0.9   550  50:50    17   17   p-type BP:H:F                        *4.2  1.0   500  50:50                                             0.72  19.1   1.2              i-type A-SiGeC:H              n-type BP:H:F                        **4.0 0.9   450  50:50    18   18   p-type BP:H:F                        *4.2  1.0   500  51:49                                             0.60  18.1   1.1              i-type poly-Si:H              n-type BP:H:F                        **4.0 0.9   450  50:50    __________________________________________________________________________     *p-type BP:H(F) film     **n-type BP:H(F) film

                  TABLE 18    ______________________________________            substrate temperature: 230° C.            flow rate of Si.sub.2 H.sub.6 gas: 8 sccm            flow rate of GeF.sub.4 gas: 6 sccm            flow rate of PH.sub.3 gas: 6 sccm            (diluted by H.sub.2 gas to 3000 ppm)            flow rate of H.sub.2 gas: 200 sccm            inner pressure: 0.8 Torr            high frequency power: 50W (13.56MHz)    ______________________________________

                  TABLE 19    ______________________________________            substrate temperature: 220° C.            flow rate of SiF.sub.4 gas: 25 sccm            flow rate of CH.sub.4 gas: 5 sccm            flow rate of H.sub.2 gas: 250 sccm            flow rate of PH.sub.3 gas: 21 sccm            (diluted by H.sub.2 gas to 3000 ppm)            inner pressure: 1.1 Torr            high frequency power: 45W (13.56MHz)    ______________________________________

                  TABLE 20    ______________________________________    target material      GaAs polycrystal wafer    substrate temperature                         220° C.    flow rate of Ar gas   50 sccm    flow rate of SiH.sub.4 gas                          5 sccm    (diluted by Ar gas to 1000 ppm)    inner pressure        5 mTorr    high frequency power 350 W (13.56 MHz)    ______________________________________

                  TABLE 21    ______________________________________    substrate temperature                        220° C.    flow rate of Si.sub.2 H.sub.6 gas                         13 sccm    flow rate of H.sub.2 gas                        250 sccm    inner pressure       1.2 Torr    high frequency power                         40 W (13.56 MHz)    ______________________________________

                  TABLE 22    ______________________________________    substrate temperature                        220° C.    flow rate of Si.sub.2 H.sub.6 gas                         15 sccm    flow rate of GeH.sub.4 gas                         8 sccm    flow rate of H.sub.2 gas                        250 sccm    inner pressure       1.0 Torr    high frequency power                         40 W (13.56 MHz)    ______________________________________

                  TABLE 23    ______________________________________            substrate temperature: 220° C.            flow rate of SiH.sub.4 gas: 50 sccm            flow rate of CH.sub.4 gas: 5 sccm            flow rate of H.sub.2 gas: 250 sccm            inner pressure: 0.5 Torr            high frequency power: 50W (13.56MHz)    ______________________________________

                  TABLE 24    ______________________________________    target material: Si single-crystal wafer    substrate temperature: 220° C.    flow rate of Ar gas: 60 sccm    flow rate of F.sub.2 gas: 50 sccm    inner pressure: 5 mTorr    high frequency power: 300W (13.56MHz)    ______________________________________

                  TABLE 25    ______________________________________    substrate temperature                        220° C.    flow rate of SiH.sub.4 gas                         50 sccm    flow rate of GeH.sub.4 gas                         40 sccm    flow rate of CH.sub.4 gas                         3 sccm    flow rate of H.sub.2 gas                        200 sccm    inner pressure       0.8 Torr    high frequency power                         50 W (13.56 MHz)    ______________________________________

                  TABLE 26    ______________________________________    target material    Si single-crystal wafer    substrate temperature                       220° C.    flow rate of Ar gas                        30 sccm    flow rate of Hz gas                        40 sccm    inner pressure      5 mTorr    high frequency power                       300 W (13.56 MHz)    ______________________________________

                                      TABLE 27    __________________________________________________________________________                                           open-circuit                                                  short-circuit                                                         output value under                        characteristics of n-type BP:H(F) film                                           voltage under                                                  photocurrent                                                         irradiation of                        hydrogen                             fluorine                                  average                                       compo-                                           irradiation of                                                  under irradia-                                                         AM-1 light (using         Element        content                             content                                  crystal                                       sition                                           AM-1 light                                                  tion of AM-1                                                         400 nm interference    Example         Sample              semiconductor                        (atomic                             (atomic                                  grain size                                       ratio of                                           Voc    light  filter)    No.  No.  layer     %)   %)   (Å)                                       B to P                                           [Volt] Isc [mA/cm.sup.2 ]                                                         [relative    __________________________________________________________________________                                                         value]    19   19   p-type A--Si:H:F                        3.9  0.9  350  50:50                                           0.95   16.8   1.4              i-type A--Si:H:F              n-type BP:H:F    20   20   p-type A--SiC:H:F                        3.9  0.9  350  49:51                                           0.96   17.7   1.6              i-type A--Si:H:F              n-type BP:H:F    21   21   p-type ZnTe                        4.0  1.0  350  50:50                                           0.93   16.9   1.2              i-type A--Si:H:F              n-type BP:H:F    22   22   p-type BP 3.9  0.9  350  50:50                                           0.97   16.7   1.3              i-type A--Si:H:F              n-type BP:H:F    __________________________________________________________________________

                  TABLE 28    ______________________________________    target material     ZnTe polycrystal wafer    substrate temperature                        220° C.    flow rate of Ar gas  50 sccm    flow rate of PH.sub.3 gas                         30 sccm    (diluted by Ar gas to 2000 ppm)    inner pressure       5 mTorr    high frequency power                        300 W (13.56 MHz)    ______________________________________

                  TABLE 29    ______________________________________    target material    BP polycrystal wafer    substrate temperature                       220° C.    flow rate of Ar gas                        50 sccm    flow rate of Ar gas                        10 sccm    for bubbling Zn(CH.sub.3).sub.3    inner pressure      5 mTorr    high frequency power                       300 W (13.56 MHz)    ______________________________________

                                      TABLE 30    __________________________________________________________________________                       open circuit                              short-circuit                                     ratio of change in the                       voltage under                              photocurrent                                     photoelectric conver-                       irradiation of                              under irradia-                                     sion efficiency after                       AM-1 light                              tion of AM-1                                     10 hours irradiation             semiconductor                       Voc    light  of AM-1 light             layer     [Volt] Isc [mA/cm.sup.2 ]                                     [Δη/η %]    __________________________________________________________________________    Example No. 23    Element Sample    No. 23    third layer             p-type BP:H:F                       2.80   11.5   2.1             i-type A--SiC:H:F             n-type A--Si:H:F    second layer             p-type BP:H:F             i-type A--Si:H:F             n-type A--Si:H:F    first layer             p-type BP:H:F             i-type A--SiGe:H:F             n-type A--Si:H:F    Comparative    example No. 5    Element Sample    No. 31    third layer             p-type A--Si:H:F                       2.40   11.8   2.9             i-type A--SiC:H:F             n-type A--Si:H:F    second layer             p-type BP:H:F             i-type A--Si:H:F             n-type A--Si:H:F    first layer             p-type BP:H:F             i-type A--SiGe:H:F             n-type A--Si:H:F    __________________________________________________________________________

                                      TABLE 31    __________________________________________________________________________                        characteristics of p-type BP:H(F) film                                       compo-                                           open-circuit                                                  short-circuit                                                         output value under                                       sition                                           voltage under                                                  photocurrent                                                         irradiation of    Com-                hydrogen                             fluorine                                  average                                       ratio of                                           irradiation of                                                  under irradia-                                                         AM-1 light (using    parative         Element        content                             content                                  crystal                                       B to P                                           AM-1 light                                                  tion of AM-1                                                         400 nm interference    Example         Sample              semiconductor                        (atomic                             (atomic                                  grain size                                       (atomic                                           Voc    light  filter)    No.  No.  layer     %)   %)   (Å)                                       %)  [Volt] Isc [mA/cm.sup.2 ]                                                         [relative    __________________________________________________________________________                                                         value]    1    24   p-type A--Si:H:F                        --   --   --   --  0.76   14.1   1.0              i-type A--Si:H:F              n-type A--Si:H:F    2    25   p-type BP:F                        --   6.6  --   32:68                                           0.30   5.9    0.11              i-type A--Si:H:F              n-type A--Si:H:F         26   p-type BP:H:F                        0.4  2.4  --   40:60                                           0.45   10.1   0.42              i-type A--Si:H:F              n-type A--Si:H:F    3    27   p-type BP:H:F                        5.0  3.5  300  31:69                                           0.65   12.1   0.70              i-type A--Si:H:F              n-type A--Si:H:F    4    28   p-type BP:H:F                        4.3  1.8  450  49:51                                           0.17   2.3    0.06              i-type A--Si              n-type A--Si:H:F         29   p-type BP:H:F                        4.4  1.2  400  50:50                                           0.06   1.0    0.03              i-type A--SiC              n-type A--Si:H:F         30   p-type BP:H:F                        4.5  1.2  400  49:51                                           0.08   0.9    0.02              i-type A--SiGe              n-type A--Si:H:F    __________________________________________________________________________

                  TABLE 32    ______________________________________               Element Sample No.    conditions   28         29        30    ______________________________________    target material                 Si         SiC       SiGe                 polycrystal                            polycrystal                                      polycrystal                 wafer      wafer     wafer    substrate temperature                 220° C.                            220° C.                                      220° C.    flow rate of Ar gas                 30 sccm    30 sccm   30 sccm    inner pressure                 4 mTorr    4 mTorr   4 mTorr    high frequency power                 320 W      320 W     320 W    (13.56 MHz)    ______________________________________

What we claim is:
 1. A pin heterojunction photovoltaic element whichgenerates photoelectromotive force by the junction of a p-typesemiconductor layer, an i-type semiconductor layer and an n-typesemiconductor layer, characterized in that at least one of said p-typeand n-type semiconductor layers comprises a polycrystal semiconductorfilm comprised of boron atoms (B), phosphorus atoms (P), hydrogen atoms(H), and atoms (M) of a p-type or n-type dopant element, saidpolycrystal semiconductor film contains crystal grains of an averagesize in the range of 50 to 800 Å, and said polycrystal semiconductorfilm contains the hydrogen atoms (H) in an amount of 0.5 to 7 atomic %;and said i-type semiconductor layer comprises a non-single crystalsemiconductor film containing silicon atoms (Si) as a matrix and atleast one kind of atoms selected from the group consisting of hydrogenatoms (H) and fluorine atoms (F).
 2. A pin hetrojunction photovoltaicelement according to claim 1, wherein said polycrystal semiconductorfilm further contains fluorine atoms (F) in an amount of 3 atomic % orless.
 3. A pin heterojunction photovoltaic element which generatesphotoelectromotive force by the junction of a p-type semiconductorlayer, an i-type semiconductor layer and n-type semiconductor layer,characterized in that at least one of said p-type and n-typesemiconductor layers comprises a polycrystal semiconductor filmcomprised of boron atoms (B), phosphorus atoms (P), hydrogen atoms (H),and atoms (M) of a p-type or n-type dopant element, said polycrystalsemiconductor film contains crystal grains of an average size in therange of 50 to 800 Å, and said polycrystal semiconductor film containsthe hydrogen atoms (H) in an amount of 0.5 to 7 atomic %; and saidi-type semiconductor layer comprises a non-single crystal semiconductorfilm containing silicon atoms (Si) as a matrix, at least one kind ofatoms selected from the group consisting of carbon atoms (C) andgermanium atoms (Ge), and at least one kind of atoms selected from thegroup consisting of hydrogen atoms (H) and fluorine atoms (F).
 4. A pinheterojunction photovoltaic element according to claim 3, wherein saidpolycrystal semiconductor film further contains fluorine atoms in anamount of 3 atomic % or less.